Spawn a new :class:`Actor` and return its
        :class:`.ActorProxyMonitor`.

def spawn(self, monitor, kind=None, **params):
        '''Spawn a new :class:`Actor` and return its
        :class:`.ActorProxyMonitor`.
        '''
        proxy = _spawn_actor(kind, monitor, **params)
        # Add to the list of managed actors if this is a remote actor
        if isinstance(proxy, Actor):
            self._register(proxy)
            return proxy
        else:
            proxy.monitor = monitor
            self.managed_actors[proxy.aid] = proxy
            future = actor_proxy_future(proxy)
            proxy.start()
            return future