https://api.drupal.org/api/drupal/core%21modules%21contact%21src%21Entity%21Message.php/function/Message%3A%3AsetSubject/9
function Message::setSubject | Drupal API
functionmessagedrupalapi
https://api.drupal.org/api/drupal/11.x/search/setSubject
Search for setSubject | Drupal API
search fordrupalapi