Error in # UNQ_C7 GRADED FUNCTION: viterbi_backward . 3/4 tets passes

I have been facing issues while running viterbi backward . Iam getting 3 tests passed, 1 failed for UNQ_C7 I tried changing the for loop range in step 2 but the issue is not resolved . Could you please look into this @Mubsi

My lab id : gzmzvydrlvxn

I am also facing the same issue. Tried stack exchange and other resources but unable to get the bug. ultimately I had to satisfy myself with 70/80 grade which in anyway enough for passing the assignment. I moved on to week 3.

In case some one has got it correctly please post hints.