Traceback (most recent call last):
  File "main.py", line 71, in <module>
    model = combined(FILENAME, AMOUNT, DEPTH, TARGET_HEIGHT, TARGET_WIDTH)
  File "/home/user1/REUS/image-reconstruction/code/functional/model_build_up.py", line 132, in combined
    combined_model = Model(inputs = ip, outputs = SRnet_layer)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/legacy/interfaces.py", line 91, in wrapper
    return func(*args, **kwargs)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/engine/network.py", line 93, in __init__
    self._init_graph_network(*args, **kwargs)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/engine/network.py", line 231, in _init_graph_network
    self.inputs, self.outputs)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/engine/network.py", line 1366, in _map_graph_network
    tensor_index=tensor_index)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/engine/network.py", line 1353, in build_map
    node_index, tensor_index)
  File "/home/user1/.conda/envs/tf-cpu/lib/python3.7/site-packages/keras/engine/network.py", line 1325, in build_map
    node = layer._inbound_nodes[node_index]
AttributeError: 'NoneType' object has no attribute '_inbound_nodes'