Error when implement ObjectDetection as API in flask

I am having an issue when trying to implement ObjectDetection as an api with Flask framework

My source code is just the simple use of ObjectDetection

@app.route("/")
def hello():
    func()
    return "Hello world"
    
def func():

    execution_path = os.getcwd()
    detector = ObjectDetection()
    detector.setModelTypeAsTinyYOLOv3()
    detector.setModelPath( os.path.join(execution_path , "yolo-tiny.h5"))
    detector.loadModel(detection_speed="fastest")

    custom_objects = detector.CustomObjects(person=True)
    image_path = "sampleImage.jpg"
    check = os.path.isfile(image_path)
    print(check)
    detections = detector.detectCustomObjectsFromImage(custom_objects=custom_objects, input_image=image_path, minimum_percentage_probability=20)

    for eachObject in detections:
        print(eachObject["name"] , " : " , eachObject["percentage_probability"] )

if __name__ == '__main__':
    app.run(debug=True)

Problem is the api only success on the first request. From second request, it comes with following error:

TypeError: Cannot interpret feed_dict key as Tensor: Tensor Tensor("Placeholder:0", shape=(3, 3, 3, 16), dtype=float32) is not an element of this graph.

Full stack trace:

Traceback (most recent call last):
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/ptoan/Desktop/object-detection/app.py", line 15, in hello
    func()
  File "/Users/ptoan/Desktop/object-detection/app.py", line 24, in func
    detector.loadModel(detection_speed="fastest")
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/imageai/Detection/__init__.py", line 213, in loadModel
    model.load_weights(self.modelPath)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/keras/engine/network.py", line 1166, in load_weights
    f, self.layers, reshape=reshape)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/keras/engine/saving.py", line 1058, in load_weights_from_hdf5_group
    K.batch_set_value(weight_value_tuples)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py", line 2470, in batch_set_value
    get_session().run(assign_ops, feed_dict=feed_dict)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/tensorflow/python/client/session.py", line 929, in run
    run_metadata_ptr)
  File "/Users/ptoan/Desktop/object-detection/venv/lib/python3.6/site-packages/tensorflow/python/client/session.py", line 1095, in _run
    'Cannot interpret feed_dict key as Tensor: ' + e.args[0])
TypeError: Cannot interpret feed_dict key as Tensor: Tensor Tensor("Placeholder:0", shape=(3, 3, 3, 16), dtype=float32) is not an element of this graph.