Pinq\ITraversable::union PHP Метод

    public function union($values);

 /**
  * @dataProvider emptyData
  */
 public function testThatUnionMaintainsReferences(\Pinq\ITraversable $traversable)
 {
     $data = $this->makeRefs(range('a', 'f'));
     $traversable->union($data)->iterate(function (&$i) {
         $i = "{$i}-";
     });
     $this->assertSame('a-b-c-d-e-f-', implode('', $data));
 }