code: def _pad_data(self, max_len=None):
          
          if not max_len:
              max_len = max([len(x) for x in self._data])
          for _, col in enumerate(self._data):
              col.extend([None] * (max_len - len(col)))
docs: Pad the data in DataFrame with [None} to ensure that all columns have the same length.
  
          :param max_len: If provided will extend all columns to this length, if not then will use the longest column
          :return: nothing