public static function by_spoken_languages($language, $format = 'array')
 {
     $value = self::filter_value($language);
     $value = WPMOLY_L10n::get_language_native_name($value);
     $meta_query = self::by_interval('spoken_languages', $value, $strict = false, $filter = false);
     if ('sql' === $format) {
         $meta_query = self::get_sql($meta_query);
     }
     return $meta_query;
 }