docs: def expand_entity(self, entity):
          """
          Search and return entity or sub entity that contain value of this field.
          :param entity:
          :return: entity
          :raise KeyError
          """
          if self.name in entity:
              return entity
          for key, value in entity.items():
              if isinstance(value, dict):
                  if self.name in value:
                      return value
          raise KeyError("The field %s (%s) not found in %s" % (self.name, self._rule['type'], entity))