code: def lookup(self, request: Request) -> List[Callable[[], Handler]]:
          
          key = request.__class__.__name__
          if key not in self._registry:
              if request.is_command():
                  raise ConfigurationException("There is no handler registered for this request")
              elif request.is_event():
                  return []  # type: Callable[[] Handler]
  
          return self._registry[key]
docs: Looks up the handler associated with a request - matches the key on the request to a registered handler
          :param request: The request we want to find a handler for
          :return: