##fileformat=VCFv4.2
##FORMAT=<ID=GT,Number=1,Type=String,Description="Genotype">
##FORMAT=<ID=PS,Number=1,Type=String,Description="Phase set, spelled as a string">
##contig=<ID=chrZ,length=1000>
#CHROM POS ID REF ALT QUAL FILTER INFO FORMAT S1
chrZ 101 . AAAAAAAA TTTTTTT . . . GT:PS 0|1:block_a
chrZ 201 . AAAAAAA TTTTT . . . GT:PS 1|1:block_a