code: def add_suffix(self, suffix):
          
          f = functools.partial('{}{suffix}'.format, suffix=suffix)
  
          mapper = {self._info_axis_name: f}
          return self.rename(**mapper)
docs: Suffix labels with string `suffix`.
  
          For Series, the row labels are suffixed.
          For DataFrame, the column labels are suffixed.
  
          Parameters
          ----------
          suffix : str
              The string to add after each label.
  
          Returns
          -------
          Series or DataFrame
              New Series or DataFrame with updated labels.
  
          See Also
          --------
          Series.add_prefix: Prefix row labels with string `prefix`.
          DataFrame.add_prefix: Prefix column labels with string `prefix`.
  
          Examples
          --------
          >>> s = pd.Series([1, 2, 3, 4])
          >>> s
          0    1
          1    2
          2    3
          3    4
          dtype: int64
  
          >>> s.add_suffix('_item')
          0_item    1
          1_item    2
          2_item    3
          3_item    4
          dtype: int64
  
          >>> df = pd.DataFrame({'A': [1, 2, 3, 4],  'B': [3, 4, 5, 6]})
          >>> df
             A  B
          0  1  3
          1  2  4
          2  3  5
          3  4  6
  
          >>> df.add_suffix('_col')
               A_col  B_col
          0       1       3
          1       2       4
          2       3       5
          3       4       6