public function sync($data = false)
    {
        if ($this->_exists !== null) {
            return;
        }
        $id = $this->id();
        if ($id !== null) {
            $persisted = static::load($id);
            if ($persisted && $data) {
                $this->amend($persisted->data(), ['exists' => true]);
            } else {
                $this->_exists = !!$persisted;
            }
        } else {
            $this->_exists = false;
        }
    }