docs: def is_instance(self, model):
          """
          Is instance?
          Checks if provided object is instance of this service's model.
  
          :param model:           object
          :return:                bool
          """
          result = isinstance(model, self.__model__)
          if result is True:
              return True
  
          err = 'Object {} is not of type {}'
          raise ValueError(err.format(model, self.__model__))