Our custom addition to the view
            adds an easy radio button choice for the new state. This is meant to be for tutors.
            We need to peel this choice from the form data and set the state accordingly.
            The radio buttons have no default, so that we can keep the existing state
            if the user makes no explicit choice.
            Everything else can be managed as prepared by the framework.

def save_model(self, request, obj, form, change):
        ''' Our custom addition to the view
            adds an easy radio button choice for the new state. This is meant to be for tutors.
            We need to peel this choice from the form data and set the state accordingly.
            The radio buttons have no default, so that we can keep the existing state
            if the user makes no explicit choice.
            Everything else can be managed as prepared by the framework.
        '''
        if 'newstate' in request.POST:
            if request.POST['newstate'] == 'finished':
                obj.state = Submission.GRADED
            elif request.POST['newstate'] == 'unfinished':
                obj.state = Submission.GRADING_IN_PROGRESS
        obj.save()