def remove_listener(listener)
      type = listener.type
      if listeners.has_key? type
        listeners[type].delete(listener)
        listeners.delete(type) if listeners[type].empty?
      end
    end
def remove_listener(listener)
      type = listener.type
      if listeners.has_key? type
        listeners[type].delete(listener)
        listeners.delete(type) if listeners[type].empty?
      end
    end
Unregister the given block. It won't be call then went an event is emitted.