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

cb	NIMQChatServerSubscribeParam
ope_type	NIMQChatServerSubscribeParam
server_ids	NIMQChatServerSubscribeParam
server_ids_count	NIMQChatServerSubscribeParam
sub_type	NIMQChatServerSubscribeParam
user_data	NIMQChatServerSubscribeParam