<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _token_auth(self):
 """Add ThreatConnect Token Auth to Session."""

        return TcExTokenAuth(
            self,
            self.args.tc_token,
            self.args.tc_token_expires,
            self.args.tc_api_path,
            self.tcex.log,
        )