protected function setLocalSessionValue($key, $value) {
    $sessionVarname = get_class($this);
    $localValues = $this->session->get($sessionVarname, null);
    if ($localValues == null) {
      $localValues = [];
    }
    $localValues[$key] = $value;
    $this->session->set($sessionVarname, $localValues);
  }