Why do i get "expected string or bytes-like object" while testing Fashion-mnist model in django with a local image?

I'm trying to deply Fashion-mnist model in a django project and found this error :"expected string or bytes-like object" when trying to test the model using predict function after doing some changes on the image (after loading it )with a local image from my computer . Here is the predict function in Views.py:

@csrf_exempt
def predict(request):
path = "D:/desktop/pullover.jpg"
im = Image.open(os.path.join(path))
convertImage(im)
x = Image.open(OUTPUT, mode='L')
x = np.invert(x)
x = Image.resize(x, (28, 28))
x = x.reshape(1, 28, 28, 1)
with graph.as_default():
    out = model.predict(x)
    print(out)
    print(np.argmax(out, axis=1))
    response = np.array_str(np.argmax(out, axis=1))
return JsonResponse({"output": response})

other functions i used in predict function in Views.py:

def getI420FromBase64(codec):
base64_data = re.sub('^data:image/.+;base64,', '', codec)
byte_data = base64.b64decode(base64_data)
image_data = BytesIO(byte_data)
img = Image.open(image_data)
img.save(OUTPUT)


def convertImage(imgData):
getI420FromBase64(imgData)

utils.py

from keras.models import model_from_json
import tensorflow as tf
import os

JSONpath = os.path.join(os.path.dirname(__file__), 'models', 'model.json')
MODELpath = os.path.join(os.path.dirname(__file__), 'models', 'mnist.h5')


def init():
json_file = open(JSONpath, 'r')
loaded_model_json = json_file.read()
json_file.close()
loaded_model = model_from_json(loaded_model_json)
loaded_model.load_weights(MODELpath)
print("Loaded Model from disk")
loaded_model.compile(loss='categorical_crossentropy',
                     optimizer='adam', metrics=['accuracy'])
# graph = tf.get_default_graph()
graph = tf.compat.v1.get_default_graph()
return loaded_model, graph

Any kind of help would be appreciated .