docs: def get_empty_results(self):
          """
          Because the base result type is different depending on the return structure
          (e.g. list for flat, dict for object), `get_result_type` initials the
          `results` variable to the proper type
          """
          assert self.result_type is not None, (
              '{} must specify a `result_type` value or overwrite the '
              '`get_empty_result` method.'.format(self.__class__.__name__)
          )
  
          return self.result_type()