code: protected function getLanguage($singleLanguage, $metaModels)
      {
          if (!empty($singleLanguage)) {
              return array($singleLanguage);
          } elseif ($metaModels->isTranslated() && $metaModels->getAvailableLanguages()) {
              return $metaModels->getAvailableLanguages();
          }
  
          return array($GLOBALS['TL_LANGUAGE']);
      }
docs: Get the language.
  
  First check the overwrite language. Then check if the MetaModels is translated and get all languages from it.
  Use the current language as fallback.
  
  @param string     $singleLanguage The language with the overwrite.
  
  @param IMetaModel $metaModels     The MetaModels for the check.
  
  @return string[] A list with all languages or null.
  
  @SuppressWarnings(PHPMD.Superglobals)
  @SuppressWarnings(PHPMD.CamelCaseVariableName)