docs: def on(self, event_name, *args, **kwargs):
          """Decorator shortcut for add_event_handler.
  
          Args:
              event_name: An event to attach the handler to. Valid events are from :class:`~ignite.engine.Events` or
                  any `event_name` added by :meth:`~ignite.engine.Engine.register_events`.
              *args: optional args to be passed to `handler`.
              **kwargs: optional keyword args to be passed to `handler`.
  
          """
          def decorator(f):
              self.add_event_handler(event_name, f, *args, **kwargs)
              return f
          return decorator