Есть ли способ вернуть несколько JSON объектов-графиков в AJAX запрос в python?

Question

Я пытаюсь вернуть несколько JSON объектов-графиков в запрос AJAX в моем приложении Flask, но получаю сообщение об ошибке

TypeError: The view function did not return a valid response tuple. The tuple must have the form (body, status, headers), (body, status), or (body, headers).

I ' я не уверен, как преобразовать графически JSON объекты в кортежи для отправки обратно на запрос AJAX. Это мой Python код:

def create_bar_plot(query, ycol, title):
    df = pd.DataFrame(query, columns=[ycol,'count'])
    data = [
        go.Bar(
            x=df['count'], 
            y=df[ycol],
            orientation='h'
        )
    ]
    layout=go.Layout(title=title, xaxis={'title':'count'}, yaxis={'type':'category'})
    figure=go.Figure(data=data,layout=layout)
    graphJSON = json.dumps(figure, cls=plotly.utils.PlotlyJSONEncoder)
    return graphJSON


@app.route('/change_visualization', methods=['GET', 'POST'])
@login_required
def change_visualization():
    """
    Change year
    """
    year = request.args['selected']
    data = []
    first_query = db.engine.execute("""SELECT machine, COUNT(*) as `count` FROM table1 WHERE id LIKE %s GROUP BY machine""", (year + '%',))
    first_result = create_bar_plot(run_info_query, "machine", "First Result")
    data.append(first_result)

    second_query = db.engine.execute("""SELECT Type, COUNT(*) as 'count' FROM table2 WHERE id LIKE %s GROUP BY Type;""", (year + '%',))
    second_result = create_bar_plot(project_type_query, "Type", "Second Result")
    data.append(second_result)

    third_query = db.engine.execute("""SELECT Type, COUNT(*) as 'count' FROM table3 WHERE id LIKE %s GROUP BY Type;""", (year + '%',))
    third_result = create_bar_plot(sample_type_query, "Type", "Third Result")
    data.append(third_result)

    return tuple(data)

И AJAX:

  <script>
    $('#year').on('change',function(){
        $.ajax({
            url: "/change_visualization",
            type: "GET",
            contentType: 'application/json;charset=UTF-8',
            data: {
                'selected': document.getElementById('year').value
            },
            dataType:"json",
            success: function (data) {
                Plotly.newPlot('bargraph1', data.first_result,{});
                Plotly.newPlot('bargraph2', data.second_result,{});
                Plotly.newPlot('bargraph3', data.third_result,{});
            }
        });
    })
  </script>

Любая помощь будет оценена