code: def _merge_user_attrs(self, attrs_backend, attrs_out, backend_name):
          
          for attr in attrs_backend:
              if attr in self.attributes.backend_attributes[backend_name]:
                  attrid = self.attributes.backend_attributes[backend_name][attr]
                  if attrid not in attrs_out:
                      attrs_out[attrid] = attrs_backend[attr]
docs: merge attributes from one backend search to the attributes dict
          output