code: def _check_result_dict_for_needed_keys(self, results_dict):
          
          missing_cols = [x for x in needed_result_keys if x not in results_dict]
          if missing_cols != []:
              msg = "The following keys are missing from results_dict\n{}"
              raise ValueError(msg.format(missing_cols))
          return None
docs: Ensure that `results_dict` has the needed keys to store all the
          estimation results. Raise a helpful ValueError otherwise.