public function toArray()
 {
     return array_diff_key(parent::toArray() + $this->persistent->toArray(), $this->removed);
 }
 public function toArray()
 {
     $result = $this->persistent->toArray();
     foreach (parent::toArray() as $k => $v) {
         $result[$k] = $v;
     }
     return array_diff_key($result, $this->removed);
 }