DOC: Resolve RT03 errors for selected methods

ci/code_checks.sh

@@ -614,15 +614,10 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
 
     MSG='Partially validate docstrings (RT03)' ;  echo $MSG
     $BASE_DIR/scripts/validate_docstrings.py --format=actions --errors=RT03 --ignore_functions \
-        pandas.DataFrame.expanding\
-        pandas.DataFrame.filter\
-        pandas.DataFrame.first_valid_index\
-        pandas.DataFrame.get\
         pandas.DataFrame.hist\
         pandas.DataFrame.infer_objects\
         pandas.DataFrame.kurt\
         pandas.DataFrame.kurtosis\
-        pandas.DataFrame.last_valid_index\
         pandas.DataFrame.mask\
         pandas.DataFrame.max\
         pandas.DataFrame.mean\

pandas/core/generic.py

@@ -4183,15 +4183,19 @@ def get(self, key, default=None):
         """
         Get item from object for given key (ex: DataFrame column).
 
-        Returns default value if not found.
+        Returns ``default`` value if not found.
 
         Parameters
         ----------
         key : object
+            Key for which item should be returned.
+        default : object, default None
+            Default value to return if key is not found.
 
         Returns
         -------
         same type as items contained in object
+            Item for given key or ``default`` value, if key is not found.
 
         Examples
         --------
@@ -5362,10 +5366,11 @@ def filter(
         axis: Axis | None = None,
     ) -> Self:
         """
-        Subset the dataframe rows or columns according to the specified index labels.
+        Subset the DataFrame or Series according to the specified index labels.
 
-        Note that this routine does not filter a dataframe on its
-        contents. The filter is applied to the labels of the index.
+        For DataFrame, filter rows or columns depending on ``axis`` argument.
+        Note that this routine does not filter based on content.
+        The filter is applied to the labels of the index.
 
         Parameters
         ----------
@@ -5378,11 +5383,13 @@ def filter(
         axis : {0 or 'index', 1 or 'columns', None}, default None
             The axis to filter on, expressed either as an index (int)
             or axis name (str). By default this is the info axis, 'columns' for
-            DataFrame. For `Series` this parameter is unused and defaults to `None`.
+            ``DataFrame``. For ``Series`` this parameter is unused and defaults to
+            ``None``.
 
         Returns
         -------
-        same type as input object
+        Same type as caller
+            The filtered subset of the DataFrame or Series.
 
         See Also
         --------
@@ -11744,11 +11751,15 @@ def _find_valid_index(self, *, how: str) -> Hashable:
     @doc(position="first", klass=_shared_doc_kwargs["klass"])
     def first_valid_index(self) -> Hashable:
         """
-        Return index for {position} non-NA value or None, if no non-NA value is found.
+        Return index for {position} non-missing value or None, if no value is found.
+
+        See the :ref:`User Guide <missing_data>` for more information
+        on which values are considered missing.
 
         Returns
         -------
         type of index
+            Index of {position} non-missing value.
 
         Examples
         --------