def _join(segments):
    """simply list by joining adjacent segments."""
    new = []
    start = segments[0][0]
    end = segments[0][1]
    for i in range(len(segments) - 1):
        if segments[i + 1][0] != segments[i][1]:
            new.append((start, end))
            start = segments[i + 1][0]
        end = segments[i + 1][1]
    new.append((start, end))
    return new
