docs: async def spawn_n(self, agent_cls, n, *args, addr=None, **kwargs):
          """Same as :meth:`~creamas.mp.MultiEnvManager.spawn`, but spawn
          :attr:`n` agents with same initialization parameters.
  
          This is a managing function for
          :meth:`~creamas.mp.MultiEnvironment.spawn_n`.
  
          .. note::
  
              Since :class:`aiomas.rpc.Proxy` objects do not seem to handle
              (re)serialization, only the addresses of the spawned agents are
              returned.
          """
          ret = await self.menv.spawn_n(agent_cls, n, *args, addr=addr, **kwargs)
          return [r[1] for r in ret]