def span_overlap(reference, target):
    """test whether two time Chromatogram objects
    overlap each other in the time domain

    Parameters
    ----------
    reference: Chromatogram
    target: Chromatogram

    Returns
    -------
    bool
    """
    cond = ((reference.start_time <= target.start_time and reference.end_time >= target.end_time) or (
        reference.start_time >= target.start_time and reference.end_time <= target.end_time) or (
            reference.start_time >= target.start_time and reference.end_time >= target.end_time and
            reference.start_time <= target.end_time) or (
                reference.start_time <= target.start_time and reference.end_time >= target.start_time) or (
                    reference.start_time <= target.end_time and reference.end_time >= target.end_time))
    return cond