def previous_series_is_sbref(seqinfo, index):
    """
    Checks if the previous series is a SBRef image
    seqinfo: list with the sequences information
    index: index of the series, so the previous series would be index-1
    """
    return (
        index > 0
        and seqinfo[index - 1].series_description.lower().endswith('_sbref')
    )