Lw\Domain\Model\User\UserId::id PHP Method

    public function id()
    {
        return $this->id;
    }

 /**
  * {@inheritdoc}
  */
 public function ofId(UserId $userId)
 {
     if (!isset($this->users[$userId->id()])) {
         return;
     }
     return $this->users[$userId->id()];
 }