Pure. MyVariant indexes variants by an HGVS g. string, so a caller holding
chromosome, position, ref and alt needs this to ask about one.
This is not variant identity
This formats a variant the way one service wants it written. It is not a
canonical variant key and it does not normalize anything. The canonical key
is (assembly, chromosome, position, ref, alt), and turning arbitrary input
into one is vcfcanon's job, not this package's.