private function getAccessToken($email, $password, $clientConfig)
    {
        $oauth2Config = $clientConfig['oauth2'];
        $accessToken = null;

        // If there is a token file, try to read it and test the found token
        try {
            $filePath = array_key_exists('token_file_path', $oauth2Config) && !empty($oauth2Config['token_file_path'])
                ? $oauth2Config['token_file_path'] : '';

            if (file_exists($filePath)) {
                $data = file_get_contents($filePath);

                if (!empty($data)) {
                    $decodedData = json_decode($data);
                    $accessToken = $decodedData->access_token;

                    return $accessToken;
                }
            }
        } catch (\Exception $e) {
        }

        return $this->createAccessToken($email, $password, $clientConfig);
    }