https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Field%21Plugin%21Field%21FieldFormatter%21LanguageFormatter.php/9
LanguageFormatter.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Field%21Plugin%21Field%21FieldFormatter%21LanguageFormatter.php/property/LanguageFormatter%3A%3AlanguageManager/9
LanguageFormatter::$languageManager | Drupal API
drupalapi