docs: async def spawn(self, agent_cls, *args, addr=None, **kwargs):
          """Spawn an agent to the environment.
  
          This is a managing function for
          :meth:`~creamas.mp.MultiEnvironment.spawn`.
  
          .. note::
  
              Since :class:`aiomas.rpc.Proxy` objects do not seem to handle
              (re)serialization, only the address of the spawned agent is
              returned.
          """
          _, addr = await self.menv.spawn(agent_cls, *args, addr=addr, **kwargs)
          return addr