<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def id(self):
 """ Return an identifier for the worker to use in logging """

        if not hasattr(self, '_id'):
            self._id = str(threading.current_thread().ident + id(self))[-6:]
        return self._id