sequence_dect 实现6个状态，即6种选择的状态机。状态机的一个极度确切的描述是它是一个有向图形，由一组节点和一组相应的转移函数组成。-sequence_dectect to six states, namely, six options the state machine. State machine of an extremely precise descr iption is that it is a directed graph, by a group of nodes and