code: public UserDataConstraintType<SecurityConstraintType<T>> getOrCreateUserDataConstraint()
     {
        Node node = childNode.getOrCreate("user-data-constraint");
        UserDataConstraintType<SecurityConstraintType<T>> userDataConstraint = new UserDataConstraintTypeImpl<SecurityConstraintType<T>>(this, "user-data-constraint", childNode, node);
        return userDataConstraint;
     }
docs: If not already created, a new <code>user-data-constraint</code> element with the given value will be created.
  Otherwise, the existing <code>user-data-constraint</code> element will be returned.
  @return  a new or existing instance of <code>UserDataConstraintType<SecurityConstraintType<T>></code>