Using tt.stack worked. Thank you. Now, I am getting the following future warning:
/usr/local/lib/python3.6/dist-packages/theano/tensor/basic.py:6611: FutureWarning: Using a non-tuple sequence for multidimensional indexing is deprecated; use `arr[tuple(seq)]` instead of `arr[seq]`. In the future this will be interpreted as an array index, `arr[np.array(seq)]`, which will result either in an error or a different result.
result[diagonal_slice] = x
Do you know why this warning is being thrown and how I can remedy this?