code: def ensure_direct_subclass(class_, of):
      
      if not is_direct_subclass(class_, of):
          raise TypeError("expected a direct subclass of %r, got %s instead" % (
              of, class_.__name__))
      return class_
docs: Check whether given class is a direct subclass of another.
  
      :param class_: Class to check
      :param of: Superclass to check against
  
      :return: ``class_``, if the check succeeds
      :raise TypeError: When the check fails
  
      .. versionadded:: 0.0.4