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

context	MQTTClient_persistence
pclear	MQTTClient_persistence
pclose	MQTTClient_persistence
pcontainskey	MQTTClient_persistence
pget	MQTTClient_persistence
pkeys	MQTTClient_persistence
popen	MQTTClient_persistence
pput	MQTTClient_persistence
premove	MQTTClient_persistence