code: def _validate_field(param, fields):
      
  
      if param.field not in fields:
          raise InvalidQueryParams(**{
              'detail': 'The sort query param value of "%s" is '
                        'invalid. That field does not exist on the '
                        'resource being requested.' % param.raw_field,
              'links': LINK,
              'parameter': PARAM,
          })
docs: Ensure the sortable field exists on the model