public function logout()
    {
        // Make sure a TGT exists
        $this->checkTgtExists();

        $this->guzzleClient->delete($this->tgtLocation);
        $this->tgtLocation = null;
        $this->tgt = null;

        // Remove the TGT storage file
        if ($this->tgtStorageLocation) {
            unlink($this->tgtStorageLocation);
        }

        return true;
    }