def get_line_starts(s):
    """Return a list containing the start index of each line in s.

    The list also contains a sentinel index for the end of the string,
    so there will be one more element in the list than there are lines
    in the string
    """
    starts = [0]

    for line in s.split('\n'):
        starts.append(starts[-1] + len(line) + 1)

    starts[-1] -= 1
    return starts