private void fillTextFieldWithExistingAssignee() {
   PickerAssignee.getExistingAssignee(originalUsers)
       .map(PickerAssignee::getLoginName)
       .ifPresent(this::fillTextFieldWithUsername);
 }
 private void updateExistingAssignee(List<PickerAssignee> users, FlowPane assignedUserPane) {
   Optional<PickerAssignee> existingAssignee = PickerAssignee.getExistingAssignee(users);
   Node existingAssigneeNode = createExistingAssigneeNode(existingAssignee);
   assignedUserPane.getChildren().add(existingAssigneeNode);
 }