docs: def attach(self, engine, log_handler, event_name):
          """Attach the logger to the engine and execute `log_handler` function at `event_name` events.
  
          Args:
              engine (Engine): engine object.
              log_handler (callable): a logging handler to execute
              event_name: event to attach the logging handler to. Valid events are from :class:`~ignite.engine.Events`
                  or any `event_name` added by :meth:`~ignite.engine.Engine.register_events`.
  
          """
          if event_name not in State.event_to_attr:
              raise RuntimeError("Unknown event name '{}'".format(event_name))
  
          engine.add_event_handler(event_name, log_handler, self, event_name)