def is_form_persisted(form):
    """
    Does the form have a model instance attached and it's not being added?
    e.g. The form is about an existing Subgoal whose data is being edited.
    """
    if form.instance and not form.instance._state.adding:
        return True
    else:
        # Either the form has no instance attached or
        # it has an instance that is being added.
        return False