def find_prev_comment(buf, (row, col)):
    predicate = lambda line: LineProperties(line).is_header
    return _find_last(buf, (row, col), predicate, reverse=True)
Returns the row of the start of the previous diffscuss comment, and the
dataset/ETHPy150Open hut8labs/diffscuss/diffscuss/support/editor.py/find_prev_comment