调用当前通过Flutter应用程序进行，该应用程序发出多部分POST请求。

Flutter代码

var request = http.MultipartRequest(
      'POST',
      Uri.parse('https://techfarmtest.herokuapp.com/upload'),
    );
    Map<String, String> headers = {"Content-type": "multipart/form-data"};
    request.files.add(
      http.MultipartFile(
        widget.selectedImage.toString(),
        widget.selectedImage.readAsBytes().asStream(),
        widget.selectedImage.lengthSync(),
        filename: widget.selectedImage.path.split('/').last,
      ),
    );
    request.headers.addAll(headers);
    var res = await request.send();
    http.Response response = await http.Response.fromStream(res);
    var data = jsonDecode(response.body);
    return data;

我打算将图像上传到后端，然后执行预测并以JSON格式检索结果，后端使用Flask编写脚本。

** flask 代码**

@app.route('/upload',methods=["POST"])
def upload_image():
    if request.method == "POST":
        imageFile = request.files['image']
        fileName = werkzeug.utils.secure_filename(imageFile.filename)
        print('\nRecieved File name : ' + imageFile.filename)
        imageFile.save('./uploadedImages/' + fileName)
        pred('./uploadedImages/fileName')
def pred(sampleFile):
    model = load_model('./model.h5')
    # model.summary()
    sample_file = sampleFile
    sample_img = image.load_img(sample_file,target_size = (256,256,3))
    sample_img = image.img_to_array(sample_img)
    sample_img = np.expand_dims(sample_img,axis=0)

    prediction_arr = model.predict(sample_img)
    result = {
        'Sample' : str(sampleFile),
        'Label' : str(class_names[prediction_arr.argmax()]),
        'Confidence' : str(prediction_arr.max())
    }
    return jsonify(result)

我目前面临的问题是我正在做一个错误的请求（400）。这是一个粗略的代码（伪代码），我已经从各种资源。有什么办法去它。