Edgecase: seqlet calling with additional flanks at the beginning of sequences

[Vejni]

Hey,

I have run into to some weird results when I had seqlets at the beginning of my sequences. Namely, when using additional_flanks = 3 with recursive seqlet calling, seqlets that with additional flanks intersected 0, were called as positive attribution seqlets, even though all their individual attributions were all negative. This behaviour disappeared when I set additional_flanks to 0.

I can try to provide some data to reproduce, but I think the issue could be in seqlets.py L 445 - 447:

start = max(start - additional_flanks, 0)
end = min(end + min_seqlet_len + additional_flanks - 1, l)
attr = X_csum[i, end-1] - X_csum[i, start-1]

Namely when start is 0, the index jumps to the last element. Or at least I don't see another place in the function that could explain this.