(defn create-index
[variant-file out-csi {:keys [shift depth] :or {shift 14 depth 5}}]
(with-open [r (vcf/reader variant-file)]
(->> {:variant-file-type (if (io-util/vcf-reader? r) :vcf :bcf)}
(csi/offsets->index (vcf/read-file-offsets r) shift depth)
(csi/write-index out-csi))))