public function testExists()
 {
     parent::testExists();
     $this->assertTrue(Product::find()->where(['(!children.int!)' => 123])->exists());
     $this->assertFalse(Product::find()->where(['(!int!)' => 555])->exists());
     $this->assertTrue(Product::find()->where(['(!children.str!)' => 'value3'])->exists());
     $this->assertFalse(Product::find()->where(['(!children.str!)' => 123])->exists());
 }