code: def register_error_handler(self, error: Union[Type[Exception], int], func: Callable) -> None:
          
          self.record_once(lambda state: state.app.register_error_handler(error, func, self.name))
docs: Add an error handler function to the blueprint.
  
          This is designed to be used on the blueprint directly, and
          has the same arguments as
          :meth:`~quart.Quart.register_error_handler`. An example usage,
  
          .. code-block:: python
  
              def not_found():
                  ...
  
              blueprint = Blueprint(__name__)
              blueprint.register_error_handler(404, not_found)