diff --git a/pandas/_libs/groupby.pyx b/pandas/_libs/groupby.pyx
index a6dbaff17e543..f5f9c06a7e4c2 100644
--- a/pandas/_libs/groupby.pyx
+++ b/pandas/_libs/groupby.pyx
@@ -243,7 +243,7 @@ def group_shift_indexer(ndarray[int64_t] out, ndarray[int64_t] labels,
         label_indexer = np.zeros((ngroups, periods), dtype=np.int64)
         with nogil:
             for i in range(N):
-                ## reverse iterator if shifting backwards
+                # reverse iterator if shifting backwards
                 ii = offset + sign * i
                 lab = labels[ii]
 
diff --git a/pandas/_libs/tslibs/conversion.pyx b/pandas/_libs/tslibs/conversion.pyx
index cf5053acb229b..8cfaa1f7b5cea 100644
--- a/pandas/_libs/tslibs/conversion.pyx
+++ b/pandas/_libs/tslibs/conversion.pyx
@@ -482,7 +482,7 @@ cdef _TSObject convert_str_to_tsobject(object ts, object tz, object unit,
 cdef inline check_overflows(_TSObject obj):
     """
     Check that we haven't silently overflowed in timezone conversion
-    
+
     Parameters
     ----------
     obj : _TSObject
@@ -577,8 +577,6 @@ cdef inline datetime _localize_pydatetime(datetime dt, tzinfo tz):
     except AttributeError:
         return dt.replace(tzinfo=tz)
 
-# ----------------------------------------------------------------------
-# Timezone Conversion
 
 cpdef inline datetime localize_pydatetime(datetime dt, object tz):
     """
@@ -607,6 +605,9 @@ cpdef inline datetime localize_pydatetime(datetime dt, object tz):
         return dt.replace(tzinfo=tz)
 
 
+# ----------------------------------------------------------------------
+# Timezone Conversion
+
 cdef inline int64_t tz_convert_tzlocal_to_utc(int64_t val, tzinfo tz):
     """
     Parameters
@@ -682,10 +683,8 @@ cpdef int64_t tz_convert_single(int64_t val, object tz1, object tz2):
 
     Returns
     -------
-    int64 converted
-
+    converted: int64
     """
-
     cdef:
         ndarray[int64_t] trans, deltas
         Py_ssize_t pos
@@ -840,9 +839,17 @@ def tz_localize_to_utc(ndarray[int64_t] vals, object tz, object ambiguous=None,
     Localize tzinfo-naive i8 to given time zone (using pytz). If
     there are ambiguities in the values, raise AmbiguousTimeError.
 
+    Parameters
+    ----------
+    vals : ndarray[int64_t]
+    tz : tzinfo or None
+    ambiguous : str, bool, or arraylike
+        If arraylike, must have the same length as vals
+    errors : {"raise", "coerce"}, default "raise"
+
     Returns
     -------
-    localized : DatetimeIndex
+    localized : ndarray[int64_t]
     """
     cdef:
         ndarray[int64_t] trans, deltas, idx_shifted