Function dedup

Lib/test/test_code.py:1358–1362

(lst, prev=object())

            yield (line, end_line, col, end_col)

def dedup(lst, prev=object()):
    for item in lst:
        if item != prev:
            yield item
            prev = item

def lines_from_postions(positions):
    return dedup(l for (l, _, _, _) in positions)