NIMSystemNotification 成员列表

成员的完整列表，这些成员属于 NIMSystemNotification,包括所有继承而来的类成员

	attachment	NIMSystemNotification
	handleStatus	NIMSystemNotification
	notificationId	NIMSystemNotification
	notifyExt	NIMSystemNotification
	postscript	NIMSystemNotification
	read	NIMSystemNotification
	sourceID	NIMSystemNotification
	targetID	NIMSystemNotification
	timestamp	NIMSystemNotification
	type	NIMSystemNotification