Method getInput

/**
 * Method to get the field input markup fora grouped list.
 * Multiselect is enabled by using the multiple attribute.
 *
 * @return  string  The field input markup.
 *
 * @since   1.7.0
 */
protected function getInput()
{
    $data = $this->getLayoutData();
    // Get the field groups.
    $data['groups'] = (array) $this->getGroups();
    return $this->getRenderer($this->layout)->render($data);
}