Error with Attention Layer for Text Summarisation

Hello all, I have been following this tutorial on how to do Text Summarisation:

However, I hit a speed bump and got the error:
# AttributeError: 'tuple' object has no attribute '_keras_shape'

When I ran the code:
attn_out, attn_states = attn_layer([encoder_outputs, decoder_outputs])
In the section where the model is being built.

Could anyone help me out? Thanks in advance!!

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