public function displayDatasourceFilterPanel(XMLElement &$wrapper, $data = null, $errors = null, $fieldnamePrefix = null, $fieldnamePostfix = null)
    {
        $wrapper->appendChild(new XMLElement('header', '<h4>' . $this->get('label') . '</h4> <span>' . $this->name() . '</span>', array(
            'data-name' => $this->get('label') . ' (' . $this->name() . ')'
        )));

        $label = Widget::Label(__('Value'));
        $input = Widget::Input('fields[filter]'.($fieldnamePrefix ? '['.$fieldnamePrefix.']' : '').'['.$this->get('id').']'.($fieldnamePostfix ? '['.$fieldnamePostfix.']' : ''), ($data ? General::sanitize($data) : null));
        $input->setAttribute('autocomplete', 'off');
        $input->setAttribute('data-search-types', 'parameters');
        $input->setAttribute('data-trigger', '{$');
        $label->appendChild($input);
        $wrapper->appendChild($label);

        $this->displayFilteringOptions($wrapper);
    }