From 12dafcf6ea8121557deba1f4c320351976cb6abb Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Sun, 6 Sep 2020 15:50:04 -0500
Subject: [PATCH 01/13] CLN: move sort_index to core/generic.py #8283

---
 pandas/core/frame.py   | 67 +++++-------------------------
 pandas/core/generic.py | 93 ++++++++++++++++++++++++++++++++++++++++++
 pandas/core/series.py  | 64 +++++------------------------
 3 files changed, 115 insertions(+), 109 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 150d6e24dbb86..3276e2bbc5a54 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -5466,62 +5466,17 @@ def sort_index(
         C  3
         d  4
         """
-        # TODO: this can be combined with Series.sort_index impl as
-        # almost identical
-
-        inplace = validate_bool_kwarg(inplace, "inplace")
-
-        axis = self._get_axis_number(axis)
-        labels = self._get_axis(axis)
-        labels = ensure_key_mapped(labels, key, levels=level)
-
-        # make sure that the axis is lexsorted to start
-        # if not we need to reconstruct to get the correct indexer
-        labels = labels._sort_levels_monotonic()
-        if level is not None:
-            new_axis, indexer = labels.sortlevel(
-                level, ascending=ascending, sort_remaining=sort_remaining
-            )
-
-        elif isinstance(labels, MultiIndex):
-            from pandas.core.sorting import lexsort_indexer
-
-            indexer = lexsort_indexer(
-                labels._get_codes_for_sorting(),
-                orders=ascending,
-                na_position=na_position,
-            )
-        else:
-            from pandas.core.sorting import nargsort
-
-            # Check monotonic-ness before sort an index
-            # GH11080
-            if (ascending and labels.is_monotonic_increasing) or (
-                not ascending and labels.is_monotonic_decreasing
-            ):
-                if inplace:
-                    return
-                else:
-                    return self.copy()
-
-            indexer = nargsort(
-                labels, kind=kind, ascending=ascending, na_position=na_position
-            )
-
-        baxis = self._get_block_manager_axis(axis)
-        new_data = self._mgr.take(indexer, axis=baxis, verify=False)
-
-        # reconstruct axis if needed
-        new_data.axes[baxis] = new_data.axes[baxis]._sort_levels_monotonic()
-
-        if ignore_index:
-            new_data.axes[1] = ibase.default_index(len(indexer))
-
-        result = self._constructor(new_data)
-        if inplace:
-            return self._update_inplace(result)
-        else:
-            return result.__finalize__(self, method="sort_index")
+        return super().sort_index(
+            axis,
+            level,
+            ascending,
+            inplace,
+            kind,
+            na_position,
+            sort_remaining,
+            ignore_index,
+            key,
+        )
 
     def value_counts(
         self,
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 93c945638a174..6780ebf6ce24f 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -40,6 +40,7 @@
     CompressionOptions,
     FilePathOrBuffer,
     FrameOrSeries,
+    IndexKeyFunc,
     JSONSerializable,
     Label,
     Level,
@@ -68,6 +69,7 @@
 from pandas.core.dtypes.common import (
     ensure_int64,
     ensure_object,
+    ensure_platform_int,
     ensure_str,
     is_bool,
     is_bool_dtype,
@@ -96,6 +98,7 @@
 import pandas.core.common as com
 from pandas.core.construction import create_series_with_explicit_dtype
 from pandas.core.flags import Flags
+from pandas.core.indexes import base as ibase
 from pandas.core.indexes.api import Index, MultiIndex, RangeIndex, ensure_index
 from pandas.core.indexes.datetimes import DatetimeIndex
 from pandas.core.indexes.period import Period, PeriodIndex
@@ -104,6 +107,7 @@
 from pandas.core.missing import find_valid_index
 from pandas.core.ops import _align_method_FRAME
 from pandas.core.shared_docs import _shared_docs
+from pandas.core.sorting import ensure_key_mapped
 from pandas.core.window import Expanding, ExponentialMovingWindow, Rolling, Window
 
 from pandas.io.formats import format as fmt
@@ -4418,6 +4422,95 @@ def sort_values(
         """
         raise AbstractMethodError(self)
 
+    def sort_index(
+        self,
+        axis=0,
+        level=None,
+        ascending: bool_t = True,
+        inplace: bool_t = False,
+        kind: str = "quicksort",
+        na_position: str = "last",
+        sort_remaining: bool_t = True,
+        ignore_index: bool_t = False,
+        key: IndexKeyFunc = None,
+    ):
+
+        inplace = validate_bool_kwarg(inplace, "inplace")
+
+        is_dataframe = isinstance(self, ABCDataFrame)
+        if is_dataframe:
+            axis = self._get_axis_number(axis)
+            labels = self._get_axis(axis)
+            labels = ensure_key_mapped(labels, key, levels=level)
+            labels = labels._sort_levels_monotonic()
+            target = labels
+        else:
+            _ = self._get_axis_number(axis)
+            index = ensure_key_mapped(self.index, key, levels=level)
+            target = index
+
+        if level is not None:
+            new_index, indexer = target.sortlevel(
+                level, ascending=ascending, sort_remaining=sort_remaining
+            )
+
+        elif isinstance(target, MultiIndex):
+            from pandas.core.sorting import lexsort_indexer
+
+            if not is_dataframe:
+                target = target._sort_levels_monotonic()
+
+            indexer = lexsort_indexer(
+                target._get_codes_for_sorting(),
+                orders=ascending,
+                na_position=na_position,
+            )
+
+        else:
+            from pandas.core.sorting import nargsort
+
+            # Check monotonic-ness before sort an index
+            # GH11080
+            if (ascending and target.is_monotonic_increasing) or (
+                not ascending and target.is_monotonic_decreasing
+            ):
+                if inplace:
+                    return
+                else:
+                    return self.copy()
+
+            indexer = nargsort(
+                target, kind=kind, ascending=ascending, na_position=na_position
+            )
+
+        if is_dataframe:
+            baxis = self._get_block_manager_axis(axis)
+            new_data = self._mgr.take(indexer, axis=baxis, verify=False)
+
+            # reconstruct axis if needed
+            new_data.axes[baxis] = new_data.axes[baxis]._sort_levels_monotonic()
+
+            if ignore_index:
+                new_data.axes[1] = ibase.default_index(len(indexer))
+
+            result = self._constructor(new_data)
+
+        else:
+            indexer = ensure_platform_int(indexer)
+            new_index = self.index.take(indexer)
+            new_index = new_index._sort_levels_monotonic()
+
+            new_values = self._values.take(indexer)
+            result = self._constructor(new_values, index=new_index)
+
+            if ignore_index:
+                result.index = ibase.default_index(len(result))
+
+        if inplace:
+            return self._update_inplace(result)
+        else:
+            return result.__finalize__(self, method="sort_index")
+
     @doc(
         klass=_shared_doc_kwargs["klass"],
         axes=_shared_doc_kwargs["axes"],
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 6cbd93135a2ca..cfdf41ff4ce05 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -3462,59 +3462,17 @@ def sort_index(
         dtype: int64
         """
 
-        # TODO: this can be combined with DataFrame.sort_index impl as
-        # almost identical
-        inplace = validate_bool_kwarg(inplace, "inplace")
-        # Validate the axis parameter
-        self._get_axis_number(axis)
-        index = ensure_key_mapped(self.index, key, levels=level)
-
-        if level is not None:
-            new_index, indexer = index.sortlevel(
-                level, ascending=ascending, sort_remaining=sort_remaining
-            )
-
-        elif isinstance(index, MultiIndex):
-            from pandas.core.sorting import lexsort_indexer
-
-            labels = index._sort_levels_monotonic()
-
-            indexer = lexsort_indexer(
-                labels._get_codes_for_sorting(),
-                orders=ascending,
-                na_position=na_position,
-            )
-        else:
-            from pandas.core.sorting import nargsort
-
-            # Check monotonic-ness before sort an index
-            # GH11080
-            if (ascending and index.is_monotonic_increasing) or (
-                not ascending and index.is_monotonic_decreasing
-            ):
-                if inplace:
-                    return
-                else:
-                    return self.copy()
-
-            indexer = nargsort(
-                index, kind=kind, ascending=ascending, na_position=na_position
-            )
-
-        indexer = ensure_platform_int(indexer)
-        new_index = self.index.take(indexer)
-        new_index = new_index._sort_levels_monotonic()
-
-        new_values = self._values.take(indexer)
-        result = self._constructor(new_values, index=new_index)
-
-        if ignore_index:
-            result.index = ibase.default_index(len(result))
-
-        if inplace:
-            self._update_inplace(result)
-        else:
-            return result.__finalize__(self, method="sort_index")
+        return super().sort_index(
+            axis,
+            level,
+            ascending,
+            inplace,
+            kind,
+            na_position,
+            sort_remaining,
+            ignore_index,
+            key,
+        )
 
     def argsort(self, axis=0, kind="quicksort", order=None) -> "Series":
         """

From c2e2cb31c8be23d97b94ef03bbcd0bf23dae461a Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Sun, 6 Sep 2020 18:56:13 -0500
Subject: [PATCH 02/13] CLN: ignore typing check in core/generic.py #8283

---
 pandas/core/generic.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 6780ebf6ce24f..4f00671adfbf8 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4461,7 +4461,7 @@ def sort_index(
                 target = target._sort_levels_monotonic()
 
             indexer = lexsort_indexer(
-                target._get_codes_for_sorting(),
+                target._get_codes_for_sorting(),  # type: ignore[attr-defined]
                 orders=ascending,
                 na_position=na_position,
             )
@@ -4501,7 +4501,9 @@ def sort_index(
             new_index = new_index._sort_levels_monotonic()
 
             new_values = self._values.take(indexer)
-            result = self._constructor(new_values, index=new_index)
+            result = self._constructor(
+                new_values, index=new_index  # type: ignore[call-arg]
+            )
 
             if ignore_index:
                 result.index = ibase.default_index(len(result))

From 909fec647367605b943ae9fb9754c2ec79b5bd33 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Sun, 6 Sep 2020 19:00:34 -0500
Subject: [PATCH 03/13] CLN: remove unused import #8283

---
 pandas/core/frame.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index d3b40e5473c79..c61cfb68989a2 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -142,7 +142,6 @@
 )
 from pandas.core.reshape.melt import melt
 from pandas.core.series import Series
-from pandas.core.sorting import ensure_key_mapped
 
 from pandas.io.common import get_filepath_or_buffer
 from pandas.io.formats import console, format as fmt

From f0958b8fdac14c97b4f7038b08aa0105d9927e10 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Mon, 7 Sep 2020 22:52:27 -0500
Subject: [PATCH 04/13] refactor

---
 pandas/core/generic.py | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 4f00671adfbf8..4cb2e064db4e2 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4436,18 +4436,10 @@ def sort_index(
     ):
 
         inplace = validate_bool_kwarg(inplace, "inplace")
-
-        is_dataframe = isinstance(self, ABCDataFrame)
-        if is_dataframe:
-            axis = self._get_axis_number(axis)
-            labels = self._get_axis(axis)
-            labels = ensure_key_mapped(labels, key, levels=level)
-            labels = labels._sort_levels_monotonic()
-            target = labels
-        else:
-            _ = self._get_axis_number(axis)
-            index = ensure_key_mapped(self.index, key, levels=level)
-            target = index
+        axis = self._get_axis_number(axis)
+        target = self._get_axis(axis) if isinstance(self, ABCDataFrame) else self.index
+        target = ensure_key_mapped(target, key, levels=level)
+        target = target._sort_levels_monotonic()
 
         if level is not None:
             new_index, indexer = target.sortlevel(
@@ -4457,11 +4449,8 @@ def sort_index(
         elif isinstance(target, MultiIndex):
             from pandas.core.sorting import lexsort_indexer
 
-            if not is_dataframe:
-                target = target._sort_levels_monotonic()
-
             indexer = lexsort_indexer(
-                target._get_codes_for_sorting(),  # type: ignore[attr-defined]
+                target._get_codes_for_sorting(),
                 orders=ascending,
                 na_position=na_position,
             )
@@ -4483,7 +4472,7 @@ def sort_index(
                 target, kind=kind, ascending=ascending, na_position=na_position
             )
 
-        if is_dataframe:
+        if isinstance(self, ABCDataFrame):
             baxis = self._get_block_manager_axis(axis)
             new_data = self._mgr.take(indexer, axis=baxis, verify=False)
 

From 3ebc89d0d09605704d520d26428a71c05c35dbf5 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Tue, 8 Sep 2020 11:15:00 -0500
Subject: [PATCH 05/13] create function get indexer

---
 pandas/core/generic.py | 57 ++++++++++++++++++++++++------------------
 1 file changed, 33 insertions(+), 24 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 4cb2e064db4e2..217731f3462de 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4422,30 +4422,16 @@ def sort_values(
         """
         raise AbstractMethodError(self)
 
-    def sort_index(
-        self,
-        axis=0,
-        level=None,
-        ascending: bool_t = True,
-        inplace: bool_t = False,
-        kind: str = "quicksort",
-        na_position: str = "last",
-        sort_remaining: bool_t = True,
-        ignore_index: bool_t = False,
-        key: IndexKeyFunc = None,
+    def _get_indexer(
+        self, target, level, ascending, kind, na_position, sort_remaining, key
     ):
-
-        inplace = validate_bool_kwarg(inplace, "inplace")
-        axis = self._get_axis_number(axis)
-        target = self._get_axis(axis) if isinstance(self, ABCDataFrame) else self.index
         target = ensure_key_mapped(target, key, levels=level)
         target = target._sort_levels_monotonic()
 
         if level is not None:
-            new_index, indexer = target.sortlevel(
+            _, indexer = target.sortlevel(
                 level, ascending=ascending, sort_remaining=sort_remaining
             )
-
         elif isinstance(target, MultiIndex):
             from pandas.core.sorting import lexsort_indexer
 
@@ -4454,23 +4440,46 @@ def sort_index(
                 orders=ascending,
                 na_position=na_position,
             )
-
         else:
             from pandas.core.sorting import nargsort
 
-            # Check monotonic-ness before sort an index
-            # GH11080
+            # Check monotonic-ness before sort an index (GH 11080)
             if (ascending and target.is_monotonic_increasing) or (
                 not ascending and target.is_monotonic_decreasing
             ):
-                if inplace:
-                    return
-                else:
-                    return self.copy()
+                return None
 
             indexer = nargsort(
                 target, kind=kind, ascending=ascending, na_position=na_position
             )
+        return indexer
+
+    def sort_index(
+        self,
+        axis=0,
+        level=None,
+        ascending: bool_t = True,
+        inplace: bool_t = False,
+        kind: str = "quicksort",
+        na_position: str = "last",
+        sort_remaining: bool_t = True,
+        ignore_index: bool_t = False,
+        key: IndexKeyFunc = None,
+    ):
+
+        inplace = validate_bool_kwarg(inplace, "inplace")
+        axis = self._get_axis_number(axis)
+        target = self._get_axis(axis)
+
+        indexer = self._get_indexer(
+            target, level, ascending, kind, na_position, sort_remaining, key
+        )
+
+        if indexer is None:
+            if inplace:
+                return
+            else:
+                return self.copy()
 
         if isinstance(self, ABCDataFrame):
             baxis = self._get_block_manager_axis(axis)

From 8cb2fecc5e3d8f8c587f8f361553e266eecdc5fc Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Tue, 8 Sep 2020 20:27:32 -0500
Subject: [PATCH 06/13] move get_indexer to sorting

---
 pandas/core/generic.py | 36 ++----------------------------------
 pandas/core/sorting.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 34 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 273123e7914d6..ccebc0aef63e1 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -107,7 +107,7 @@
 from pandas.core.missing import find_valid_index
 from pandas.core.ops import align_method_FRAME
 from pandas.core.shared_docs import _shared_docs
-from pandas.core.sorting import ensure_key_mapped
+from pandas.core.sorting import ensure_key_mapped, get_indexer_indexer
 from pandas.core.window import Expanding, ExponentialMovingWindow, Rolling, Window
 
 from pandas.io.formats import format as fmt
@@ -4422,38 +4422,6 @@ def sort_values(
         """
         raise AbstractMethodError(self)
 
-    def _get_indexer(
-        self, target, level, ascending, kind, na_position, sort_remaining, key
-    ):
-        target = ensure_key_mapped(target, key, levels=level)
-        target = target._sort_levels_monotonic()
-
-        if level is not None:
-            _, indexer = target.sortlevel(
-                level, ascending=ascending, sort_remaining=sort_remaining
-            )
-        elif isinstance(target, MultiIndex):
-            from pandas.core.sorting import lexsort_indexer
-
-            indexer = lexsort_indexer(
-                target._get_codes_for_sorting(),
-                orders=ascending,
-                na_position=na_position,
-            )
-        else:
-            from pandas.core.sorting import nargsort
-
-            # Check monotonic-ness before sort an index (GH 11080)
-            if (ascending and target.is_monotonic_increasing) or (
-                not ascending and target.is_monotonic_decreasing
-            ):
-                return None
-
-            indexer = nargsort(
-                target, kind=kind, ascending=ascending, na_position=na_position
-            )
-        return indexer
-
     def sort_index(
         self,
         axis=0,
@@ -4471,7 +4439,7 @@ def sort_index(
         axis = self._get_axis_number(axis)
         target = self._get_axis(axis)
 
-        indexer = self._get_indexer(
+        indexer = get_indexer_indexer(
             target, level, ascending, kind, na_position, sort_remaining, key
         )
 
diff --git a/pandas/core/sorting.py b/pandas/core/sorting.py
index d03b2f29521b7..7103655816295 100644
--- a/pandas/core/sorting.py
+++ b/pandas/core/sorting.py
@@ -25,6 +25,34 @@
 _INT64_MAX = np.iinfo(np.int64).max
 
 
+def get_indexer_indexer(
+    target, level, ascending, kind, na_position, sort_remaining, key
+):
+
+    target = ensure_key_mapped(target, key, levels=level)
+    target = target._sort_levels_monotonic()
+
+    if level is not None:
+        _, indexer = target.sortlevel(
+            level, ascending=ascending, sort_remaining=sort_remaining
+        )
+    elif isinstance(target, ABCMultiIndex):
+        indexer = lexsort_indexer(
+            target._get_codes_for_sorting(), orders=ascending, na_position=na_position,
+        )
+    else:
+        # Check monotonic-ness before sort an index (GH 11080)
+        if (ascending and target.is_monotonic_increasing) or (
+            not ascending and target.is_monotonic_decreasing
+        ):
+            return None
+
+        indexer = nargsort(
+            target, kind=kind, ascending=ascending, na_position=na_position
+        )
+    return indexer
+
+
 def get_group_index(labels, shape, sort: bool, xnull: bool):
     """
     For the particular label_list, gets the offsets into the hypothetical list

From a035fbd340897ea92f05dd58450feb3b1be33d44 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Tue, 8 Sep 2020 20:45:51 -0500
Subject: [PATCH 07/13] remove unused import

---
 pandas/core/generic.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index ccebc0aef63e1..3b3b218190f14 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -107,7 +107,7 @@
 from pandas.core.missing import find_valid_index
 from pandas.core.ops import align_method_FRAME
 from pandas.core.shared_docs import _shared_docs
-from pandas.core.sorting import ensure_key_mapped, get_indexer_indexer
+from pandas.core.sorting import get_indexer_indexer
 from pandas.core.window import Expanding, ExponentialMovingWindow, Rolling, Window
 
 from pandas.io.formats import format as fmt

From 9691439946dd8e6c6c7acbe3dd7a3f7cee3fea18 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Wed, 9 Sep 2020 11:11:50 -0500
Subject: [PATCH 08/13] fix type import

---
 pandas/core/generic.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 17fd3d52fb891..b7bc3d9a11f62 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -40,6 +40,7 @@
     CompressionOptions,
     FilePathOrBuffer,
     FrameOrSeries,
+    IndexKeyFunc,
     IndexLabel,
     JSONSerializable,
     Label,

From c79cd8176ffb12eed6d90febaa43ed258a48cd4f Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 11 Sep 2020 13:28:51 -0500
Subject: [PATCH 09/13] simplify sort_index

---
 pandas/core/generic.py | 29 ++++++++---------------------
 1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index b7bc3d9a11f62..9074cfc824daa 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4450,30 +4450,17 @@ def sort_index(
             else:
                 return self.copy()
 
-        if isinstance(self, ABCDataFrame):
-            baxis = self._get_block_manager_axis(axis)
-            new_data = self._mgr.take(indexer, axis=baxis, verify=False)
-
-            # reconstruct axis if needed
-            new_data.axes[baxis] = new_data.axes[baxis]._sort_levels_monotonic()
-
-            if ignore_index:
-                new_data.axes[1] = ibase.default_index(len(indexer))
-
-            result = self._constructor(new_data)
+        baxis = self._get_block_manager_axis(axis)
+        new_data = self._mgr.take(indexer, axis=baxis, verify=False)
 
-        else:
-            indexer = ensure_platform_int(indexer)
-            new_index = self.index.take(indexer)
-            new_index = new_index._sort_levels_monotonic()
+        # reconstruct axis if needed
+        new_data.axes[baxis] = new_data.axes[baxis]._sort_levels_monotonic()
 
-            new_values = self._values.take(indexer)
-            result = self._constructor(
-                new_values, index=new_index  # type: ignore[call-arg]
-            )
+        if ignore_index:
+            axis = 1 if isinstance(self, ABCDataFrame) else 0
+            new_data.axes[axis] = ibase.default_index(len(indexer))
 
-            if ignore_index:
-                result.index = ibase.default_index(len(result))
+        result = self._constructor(new_data)
 
         if inplace:
             return self._update_inplace(result)

From 8b9732a3eb33e6e580b872462c22f95bb30ff999 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 11 Sep 2020 13:48:25 -0500
Subject: [PATCH 10/13] add doc string

---
 pandas/core/sorting.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/pandas/core/sorting.py b/pandas/core/sorting.py
index 7103655816295..0c315b52c2cb3 100644
--- a/pandas/core/sorting.py
+++ b/pandas/core/sorting.py
@@ -28,6 +28,24 @@
 def get_indexer_indexer(
     target, level, ascending, kind, na_position, sort_remaining, key
 ):
+    """
+    Helper method that return the indexer according to input parameters for
+    the sort_index method of DataFrame and Series.
+
+    Parameters
+    ----------
+    target : Index
+    level : int or level name or list of ints or list of level names
+    ascending : bool or list of bools, default True
+    kind : {'quicksort', 'mergesort', 'heapsort'}, default 'quicksort'
+    na_position : {'first', 'last'}, default 'last'
+    sort_remaining : bool, default True
+    key : callable, optional
+    Returns
+    -------
+    Optional[ndarray]
+        The indexer for the new index.
+    """
 
     target = ensure_key_mapped(target, key, levels=level)
     target = target._sort_levels_monotonic()

From 4461b7bc0d1562011d2f48ab4b5592d347f585a1 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Fri, 11 Sep 2020 14:14:10 -0500
Subject: [PATCH 11/13] remove unused import

---
 pandas/core/generic.py | 1 -
 pandas/core/sorting.py | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 9074cfc824daa..24eec022c0d26 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -70,7 +70,6 @@
 from pandas.core.dtypes.common import (
     ensure_int64,
     ensure_object,
-    ensure_platform_int,
     ensure_str,
     is_bool,
     is_bool_dtype,
diff --git a/pandas/core/sorting.py b/pandas/core/sorting.py
index 0c315b52c2cb3..c383d3a5db0fd 100644
--- a/pandas/core/sorting.py
+++ b/pandas/core/sorting.py
@@ -41,6 +41,7 @@ def get_indexer_indexer(
     na_position : {'first', 'last'}, default 'last'
     sort_remaining : bool, default True
     key : callable, optional
+
     Returns
     -------
     Optional[ndarray]

From 15d7401f1255a2bebb8e1be48fb6cf7d32c9ab10 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Sun, 13 Sep 2020 20:37:52 -0500
Subject: [PATCH 12/13] type get indexer

---
 pandas/core/sorting.py | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/pandas/core/sorting.py b/pandas/core/sorting.py
index c383d3a5db0fd..e87f0a0e8865d 100644
--- a/pandas/core/sorting.py
+++ b/pandas/core/sorting.py
@@ -1,6 +1,15 @@
 """ miscellaneous sorting / groupby utilities """
 from collections import defaultdict
-from typing import TYPE_CHECKING, Callable, DefaultDict, Iterable, List, Optional, Tuple
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    DefaultDict,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+    Union,
+)
 
 import numpy as np
 
@@ -20,14 +29,20 @@
 from pandas.core.construction import extract_array
 
 if TYPE_CHECKING:
-    from pandas.core.indexes.base import Index  # noqa:F401
+    from pandas.core.indexes.base import Index
 
 _INT64_MAX = np.iinfo(np.int64).max
 
 
 def get_indexer_indexer(
-    target, level, ascending, kind, na_position, sort_remaining, key
-):
+    target: "Index",
+    level: Union[str, int, List[str], List[int]],
+    ascending: bool,
+    kind: str,
+    na_position: str,
+    sort_remaining: bool,
+    key: Optional[Callable],
+) -> Optional[np.array]:
     """
     Helper method that return the indexer according to input parameters for
     the sort_index method of DataFrame and Series.

From 58a62eeb723343c35b2545c188c493fa9cb7c652 Mon Sep 17 00:00:00 2001
From: Fangchen Li <fangchen.li@outlook.com>
Date: Sun, 13 Sep 2020 20:48:51 -0500
Subject: [PATCH 13/13] fix type

---
 pandas/core/sorting.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/core/sorting.py b/pandas/core/sorting.py
index e87f0a0e8865d..dd6aadf570baa 100644
--- a/pandas/core/sorting.py
+++ b/pandas/core/sorting.py
@@ -15,6 +15,7 @@
 
 from pandas._libs import algos, hashtable, lib
 from pandas._libs.hashtable import unique_label_indices
+from pandas._typing import IndexKeyFunc
 
 from pandas.core.dtypes.common import (
     ensure_int64,
@@ -41,7 +42,7 @@ def get_indexer_indexer(
     kind: str,
     na_position: str,
     sort_remaining: bool,
-    key: Optional[Callable],
+    key: IndexKeyFunc,
 ) -> Optional[np.array]:
     """
     Helper method that return the indexer according to input parameters for