code: def _finalize(self, all_msg_errors=None):
          
          if all_msg_errors is None:
              all_msg_errors = []
  
          for key in self.stored():
              try:
                  getattr(self, key)
              except (ValueError, TypeError) as err:
                  all_msg_errors.append(err.args[0])
  
          # Raises a list of all the missing entries
          if all_msg_errors:
              raise ValueError(all_msg_errors)
docs: Access all the instance descriptors
  
          This wil trigger an exception if a required
          parameter is not set