Write a MATLAB or Python function vis_conv(A, B) that takes as input two discrete 1D signals A and B (e.g., vis_conv([1 4 2],[2 9 3 1 3])), plots A and B in 2 subplots, then visualizes, in a 3rd subplot, how B is flipped and shifted, which is then multiplied by A and the result is summed to produce and visualizes, in subplot 4, the final output as it is being updated.