private function isMappingConfigurable($mapping = NULL, $module = 'ldap_user') {
    $configurable = (
      (
        (!isset($mapping['configurable_to_drupal']) && !isset($mapping['configurable_to_ldap'])) ||
        (isset($mapping['configurable_to_drupal']) && $mapping['configurable_to_drupal']) ||
        (isset($mapping['configurable_to_ldap']) && $mapping['configurable_to_ldap'])
      )
      &&
      (
        !isset($mapping['config_module']) ||
        (isset($mapping['config_module']) && $mapping['config_module'] == $module)
      )
    );
    return $configurable;
  }