Pretrained retinanet model with Keras. SavedModel file does not exist at: "path"/"file".h5/{saved_model.pbtxt|saved_model.pb}

Question

I'm trying to load a pretrained retinanet model with keras by running:

# import keras
import keras

# import keras_retinanet
from keras_retinanet import models
from keras_retinanet.utils.image import read_image_bgr, preprocess_image, resize_image
from keras_retinanet.utils.visualization import draw_box, draw_caption
from keras_retinanet.utils.colors import label_color


# set tf backend to allow memory to grow, instead of claiming everything
import tensorflow as tf

def get_session():
    config = tf.ConfigProto()
    config.gpu_options.allow_growth = True
    return tf.Session(config=config)
model_path = os.path.join('sample_data/snapshots', sorted(os.listdir('sample_data/snapshots'), reverse=True)[0])
print(model_path)


# load retinanet model
model = models.load_model(model_path, backbone_name='resnet50')

model = models.convert_model(model)

I am facing the following error with both codes:

OSError: SavedModel file does not exist at: sample_data/snapshots/training_5000(640_480).h5/{saved_model.pbtxt|saved_model.pb}

the cause might be some new versions of Keras or tensorflow, soo I am going to list the versions that I am currently using.

keras.__version__
2.4.3

tf.__version__
2.4.1

Note: I am trying to run this code in my Colab.