SessionHandlerInterface::read PHP Method

    public function read($session_id);

 /**
  * {@inheritdoc}
  */
 public function read($session_id)
 {
     $trace = \Drupal::service('session_test.session_handler_proxy_trace');
     $trace[] = ['BEGIN', $this->optionalArgument, __FUNCTION__, $session_id];
     $result = $this->sessionHandler->read($session_id);
     $trace[] = ['END', $this->optionalArgument, __FUNCTION__, $session_id];
     return $result;
 }