code: def remove_event_handler(self, handler, event_name):
          
          if event_name not in self._event_handlers:
              raise ValueError("Input event name '{}' does not exist".format(event_name))
  
          new_event_handlers = [(h, args, kwargs) for h, args, kwargs in self._event_handlers[event_name]
                                if h != handler]
          if len(new_event_handlers) == len(self._event_handlers[event_name]):
              raise ValueError("Input handler '{}' is not found among registered event handlers".format(handler))
          self._event_handlers[event_name] = new_event_handlers
docs: Remove event handler `handler` from registered handlers of the engine
  
          Args:
              handler (callable): the callable event handler that should be removed
              event_name: The event the handler attached to.