code: def _add_updated_at_column(self, values):
          
          if not self._model.uses_timestamps():
              return values
  
          column = self._model.get_updated_at_column()
  
          if "updated_at" not in values:
              values.update({column: self._model.fresh_timestamp_string()})
  
          return values
docs: Add the "updated_at" column to a dictionary of values.
  
          :param values: The values to update
          :type values: dict
  
          :return: The new dictionary of values
          :rtype: dict