docs: def new_mapper(agent):
      """Creates a mapper object on witch add_mapping() and remove_mapping()
      can be called. It uses fire-and-forget notifications so it has a very
      low overhead and latency but a little less guarantees."""
      recp = recipient.Broadcast(MappingUpdatesPoster.protocol_id, 'lobby')
      return agent.initiate_protocol(MappingUpdatesPoster, recp)