Colab - doesn't support Tensorflow1.x any longer -- fail running in hierarchical_probabilistic_unet

Hi

Thanks for providing the notebook in colab for using hierarchical_probabilistic_unet. However, colab no longer supports Tensorflow1x any more and so it failed to run the notebook. Any advice for solution?

Best
Stella

Open the Colab notebook for hierarchical_probabilistic_unet and first reproduce the reported failure in the current Colab environment. Check the notebook's TensorFlow 1.x dependency and determine the supported path forward; done means the notebook runs successfully in Colab without the reported compatibility failure.

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