Declare a new actor on this broker.  Declaring an Actor
        twice replaces the first actor with the second by name.

        Parameters:
          actor(Actor): The actor being declared.

def declare_actor(self, actor):  # pragma: no cover
        """Declare a new actor on this broker.  Declaring an Actor
        twice replaces the first actor with the second by name.

        Parameters:
          actor(Actor): The actor being declared.
        """
        self.emit_before("declare_actor", actor)
        self.declare_queue(actor.queue_name)
        self.actors[actor.actor_name] = actor
        self.emit_after("declare_actor", actor)