code: def fields(self, fields):
          
  
          if not isinstance(fields, list):
              raise InvalidUsage('fields must be of type `list`')
  
          self._sysparms['sysparm_fields'] = ",".join(fields)
docs: Sets `sysparm_fields` after joining the given list of `fields`
  
          :param fields: List of fields to include in the response
          :raise:
              :InvalidUsage: if fields is of an unexpected type