protected function prepareFilterValues(FormInterface $form)
    {
        $config = $form->getConfig();
        $values = $this->dataExtractor->extractData($form, $config->getOption('data_extraction_method', 'default'));

        if ($config->hasAttribute('filter_options')) {
            $values = array_merge($values, $config->getAttribute('filter_options'));
        }

        return $values;
    }