def __init_subclass__(cls, **kwargs):
    """Called when a class inherits from Prefab. We use it to perform checks.
    """
    super().__init_subclass__(**kwargs)
    if not hasattr(cls, 'description'):
      raise TypeError(
          f"Class {cls.__name__} must define the 'description' class attribute."
      )
Called when a class inherits from Prefab. We use it to perform checks.
    
concordia/typing/prefab.py