code: def app_template_filter(self, name: Optional[str]=None) -> Callable:
          
          def decorator(func: Callable) -> Callable:
              self.add_app_template_filter(func, name=name)
              return func
          return decorator
docs: Add an application wide template filter.
  
          This is designed to be used as a decorator, and has the same arguments
          as :meth:`~quart.Quart.template_filter`. An example usage,
  
          .. code-block:: python
  
              blueprint = Blueprint(__name__)
              @blueprint.app_template_filter()
              def filter(value):
                  ...