(NotImplementedError: Cannot convert a symbolic Tensor (cond_2/strided_slice:0) to a numpy array.) Error in Faster rcnn

we faced a problem with running the training cell in Faster rcnn notebook : Google Colab

It was working with bad results, but now it is not working at all. I attached 2 screenshots, one is for the training cell and the other is for the error(the last line in output)

Is there anyone who got the error? please help


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