Backend\Form\Type\MetaType::buildView PHP Method

    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        if ($view->parent === null) {
            throw new LogicException('The MetaType is not a stand alone type, it needs to be used in a parent form');
        }
        if (!isset($view->parent->children[$options['base_field_name']])) {
            throw new InvalidArgumentException('The base_field_name does not exist in the parent form');
        }
        $view->vars['base_field_selector'] = '#' . $view->parent->children[$options['base_field_name']]->vars['id'];
        $view->vars['custom_meta_tags'] = $options['custom_meta_tags'];
        $view->vars['generate_url_callback_class'] = $options['generate_url_callback_class'];
        $view->vars['generate_url_callback_method'] = $options['generate_url_callback_method'];
        $view->vars['generate_url_callback_parameters'] = serialize($options['generate_url_callback_parameters']);
    }