<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def session(self):
 """A context manager for this client's session. This function closes the current session when this client goes out of scope. """

        self._session = requests.session()
        yield
        self._session.close()
        self._session = None