atk4\data\Persistence::serializeLoadField PHP Method

    public function serializeLoadField(Field $f, $value)
    {
        // use $f->serialize = [encode_callback, decode_callback]
        if (is_array($f->serialize) && isset($f->serialize[1]) && is_callable($t = $f->serialize[1])) {
            return $t($f, $value, $this);
        }
        // run persistence-specific un-serialization of field value
        return $this->_serializeLoadField($f, $value);
    }