code: def context_processor(self, func: Callable, name: AppOrBlueprintKey=None) -> Callable:
          
          self.template_context_processors[name].append(ensure_coroutine(func))
          return func
docs: Add a template context processor.
  
          This is designed to be used as a decorator. An example usage,
  
          .. code-block:: python
  
              @app.context_processor
              def update_context(context):
                  return context