Odd moodlecheck warnings for complete phpdoc

/**

  * Returns an array of warnings from the cache API.

  *

  * The warning returned here are for things like conflicting store instance configurations etc.

  * These get shown on the admin notifications page for example.

  *

  * @param array|null $stores An array of stores to get warnings for, or null for all.

  * @return string[]

  */

 public static function warnings(array $stores = null) {