def _expand_alts_in_vcf_record_list(cls, vcf_records):
        '''Input: list of vcf_records. Returns new list, where
        any records with >ALT is replaced with one vcf record per ALT.
        This doesn't change FORMAT or INFO columns, which means they
        are now broken for those records'''
        new_vcf_records = []
        for record in vcf_records:
            new_vcf_records.extend(record.to_record_per_alt())
        return new_vcf_records
Input: list of vcf_records. Returns new list, where
        any records with >ALT is replaced with one vcf record per ALT.
        This doesn't change FORMAT or INFO columns, which means they
        are now broken for those records