code: def resolve_topic(topic):
      
      try:
          module_name, _, class_name = topic.partition('#')
          module = importlib.import_module(module_name)
      except ImportError as e:
          raise TopicResolutionError("{}: {}".format(topic, e))
      try:
          cls = resolve_attr(module, class_name)
      except AttributeError as e:
          raise TopicResolutionError("{}: {}".format(topic, e))
      return cls
docs: Return class described by given topic.
  
      Args:
          topic: A string describing a class.
  
      Returns:
          A class.
  
      Raises:
          TopicResolutionError: If there is no such class.