How to use the ramp-frontend.ramp_frontend.forms.UploadForm function in ramp-frontend

code_form_kwargs[f_field] = submission_file.get_code()
    code_form_kwargs['prefix'] = 'code'
    code_form = CodeForm(**code_form_kwargs)
    # Then, to be able to iterate over the files in the sandbox.html
    # template, we also fill a separate table of pairs (file name, code).
    # The text areas in the template will then have to be created manually.
    for submission_file in sandbox_submission.files:
        if submission_file.is_editable:
            code_form.names_codes.append(
                (submission_file.name, submission_file.get_code()))

    # initialize the submission field and the the uploading form
    submit_form = SubmitForm(
        submission_name=event_team.last_submission_name, prefix='submit'
    )
    upload_form = UploadForm(prefix='upload')

    admin = is_admin(db.session, event_name, flask_login.current_user.name)
    if request.method == 'GET':
        return render_template(
            'sandbox.html',
            submission_names=sandbox_submission.f_names,
            code_form=code_form,
            submit_form=submit_form, upload_form=upload_form,
            event=event,
            admin=admin
        )

    if request.method == 'POST':
        if ('code-csrf_token' in request.form and
                code_form.validate_on_submit()):
            try: