"List index of out of range error " during inference ( Show up this week )

Question

i have been using same notebook on colab for more than 2 months with same weights and dependencies. It started to give me error this week. I didn't change anything. It suprisingly started to give me error. while loading the model. Could you please help me ?

IndexError                                Traceback (most recent call last)
<ipython-input-10-d80d5bc75b82> in <module>()
      3 
      4 # load retinanet model
----> 5 model = models.load_model(model_path, backbone_name='resnet50')
      6 model = models.convert_model(model)
      7 

8 frames
/usr/local/lib/python3.7/dist-packages/tensorflow/python/keras/engine/functional.py in process_node(layer, node_data)
   1222           add_unprocessed_node(layer, node_data)
   1223           return
-> 1224         inbound_node = inbound_layer._inbound_nodes[inbound_node_index]
   1225         input_tensors.append(
   1226             nest.flatten(inbound_node.outputs)[inbound_tensor_index])

IndexError: list index out of range

Here is the repo ( Fizyr_Keras_retinanet) :https://github.com/fizyr/keras-retinanet enter image description here