/**
  * Sanitize code textareas
  * @since  1.0.2
  * @param  string $meta  Meta value
  * @param  array  $field Field config array
  * @return string        Sanitized data
  */
 public static function file($meta, $field)
 {
     $_id_name = $field['id'] . '_id';
     // get _id old value
     $_id_old = cmb_Meta_Box::get_data($_id_name);
     // If specified NOT to save the file ID
     if (isset($field['save_id']) && !$field['save_id']) {
         $_new_id = '';
     } else {
         // otherwise get the file ID
         $_new_id = isset($_POST[$_id_name]) ? $_POST[$_id_name] : null;
         // If there is no ID saved yet, try to get it from the url
         if (isset($_POST[$field['id']]) && $_POST[$field['id']] && !$_new_id) {
             $_new_id = cmb_Meta_Box::image_id_from_url(esc_url_raw($_POST[$field['id']]));
         }
     }
     if ($_new_id && $_new_id != $_id_old) {
         $updated[] = $_id_name;
         cmb_Meta_Box::update_data($_new_id, $_id_name);
     } elseif ('' == $_new_id && $_id_old) {
         $updated[] = $_id_name;
         cmb_Meta_Box::remove_data($_id_name, $old);
     }
     return self::default_sanitization($meta, $field);
 }