Week 1 Assignment 1 RNN_backward Exercise 6 - x1 cannot be unpacked

I am currently stuck on the same place for few hours, the comment said i need to unpack the n_x, and m from the x1’s shape, but the notebook said x1 is a list thus doesn’t have shape attribute? I don’t really understand how to solve this

I think rnn_backward() itself seems to be OK.
As you see, x1 is extracted from caches, which is actually created by rnn_forward(). And, x1 is packed in rnn_foward_cell(). So, it is better to check rnn_forward functions to see a proper x is set into a cache or not.

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I am also thinking the X1 variable is a list not a numpy array.