code: def errorhandler(self, error: Union[Type[Exception], int]) -> Callable:
          
          def decorator(func: Callable) -> Callable:
              self.register_error_handler(error, func)
              return func
          return decorator
docs: Add an error handler function to the Blueprint.
  
          This is designed to be used as a decorator, and has the same
          arguments as :meth:`~quart.Quart.errorhandler`. It applies
          only to errors that originate in routes in this blueprint. An
          example usage,
  
          .. code-block:: python
  
              blueprint = Blueprint(__name__)
              @blueprint.errorhandler(404)
              def not_found():
                  ...