/**
  * Generate a token to authenticate a user
  *
  * @return mixed
  */
 public function login($device_id = null, $device_type = null, $device_token = null)
 {
     // clear old sessions for any user with: same(device_id, os)
     $to_remove = Token::where('device_id', '=', $device_id)->where('device_os', '=', $device_type)->delete();
     $token = Token::getInstance();
     $token->user_id = $this->_id;
     $token->device_id = $device_id;
     $token->device_os = $device_type;
     $token->device_token = $device_token;
     $token->save();
     return $token;
 }
 /**
  * undocumented function
  *
  * @return void
  * @author
  **/
 private function set_token()
 {
     $this->token = Token::getInstance();
 }