def variant_id_split(record):
    """Create a unique ID for each variant so they can be compared
    If multiple variant alleles, split them up.
    Args:
        record (pyvcf record)
    Returns:
        list of variant id strings
    """
    all_variant_ids = []
    POSstr = '{0:09d}'.format(record.POS) # add leading 0s
    for alt_allele in record.ALT:
        all_variant_ids.append('_'.join([str(x) for x in [record.CHROM, POSstr,
                                        record.REF, alt_allele]]))
    return all_variant_ids