/**
  *
  * @param ProjectModel $projectModel
  * @param string $userId
  * @param string $id entry id
  * @return string activity id
  */
 public static function deleteEntry($projectModel, $userId, $id)
 {
     $activity = new ActivityModel($projectModel);
     $activity->userRef->id = $userId;
     $activity->action = ActivityModel::DELETE_ENTRY;
     $lexeme = LexEntryCommands::getEntryLexeme($projectModel->id->asString(), $id);
     $activity->addContent(ActivityModel::ENTRY, $lexeme);
     return $activity->write();
 }