Add 'See also' sections (pandas-dev#17223)

pandas/core/generic.py

@@ -3681,6 +3681,9 @@ def astype(self, dtype, copy=True, errors='raise', **kwargs):
 
         See also
         --------
+        pandas.to_datetime : Convert argument to datetime.
+        pandas.to_timedelta : Convert argument to timedelta.
+        pandas.to_numeric : Convert argument to a numeric type.
         numpy.ndarray.astype : Cast a numpy array to a specified type.
         """
         if is_dict_like(dtype):

pandas/core/tools/datetimes.py

@@ -335,6 +335,10 @@ def to_datetime(arg, errors='raise', dayfirst=False, yearfirst=False,
     1    1960-01-03
     2    1960-01-04
 
+    See also
+    --------
+    pandas.DataFrame.astype : Cast argument to a specified dtype.
+    pandas.to_timedelta : Convert argument to timedelta.
     """
     from pandas.core.indexes.datetimes import DatetimeIndex
 

pandas/core/tools/numeric.py

@@ -84,6 +84,13 @@ def to_numeric(arg, errors='raise', downcast=None):
     2    2.0
     3   -3.0
     dtype: float64
+
+    See also
+    --------
+    pandas.DataFrame.astype : Cast argument to a specified dtype.
+    pandas.to_datetime : Convert argument to datetime.
+    pandas.to_timedelta : Convert argument to timedelta.
+    numpy.ndarray.astype : Cast a numpy array to a specified type.
     """
     if downcast not in (None, 'integer', 'signed', 'unsigned', 'float'):
         raise ValueError('invalid downcasting method provided')

pandas/core/tools/timedeltas.py

@@ -61,6 +61,11 @@ def to_timedelta(arg, unit='ns', box=True, errors='raise'):
     >>> pd.to_timedelta(np.arange(5), unit='d')
     TimedeltaIndex(['0 days', '1 days', '2 days', '3 days', '4 days'],
                    dtype='timedelta64[ns]', freq=None)
+
+    See also
+    --------
+    pandas.DataFrame.astype : Cast argument to a specified dtype.
+    pandas.to_datetime : Convert argument to datetime.
     """
     unit = _validate_timedelta_unit(unit)