Nelmio\Alice\Definition\Value\UniqueValue::getId PHP Method

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

 public function add(UniqueValue $value)
 {
     $valueId = $value->getId();
     if (false === array_key_exists($valueId, $this->pool)) {
         $this->pool[$valueId] = [];
     }
     $this->pool[$valueId][] = $value->getValue();
 }