Typo in hook_permission()

There is a typo in the hook_permissions() implementation as it contains two underscores and it is not picked up by Drupal.

/**
 * Implements hook_permission().
 */
function rest_api_doc__permission() {
  return array(
    'access rest_api_doc' => array(
      'title' => t('Access REST API documentation'),
      'description' => t('Allow to the user to access the REST API documentation.'),
    ),
    'administer rest_api_doc' => array(
      'title' => t('Administer REST API documentation'),
      'description' => t('Allow to the user to administer the REST API documentation.'),
    ),
  );
}