wnstream software because
the VCF specification does not allow sites with the position 0. By default
<code>ts_vcf</code> automatically transforms a site with a zero coordinate to
a coordinate 1. Setting <code>position_transform</code> to NULL will disable
this, and <code>tsv_vcf</code> will save coordinates in their original form.
See this discussion for more detail:
<a href="https://github.com/tskit-dev/tskit/issues/2838#issuecomment-1931796988" class="external-link">https://github.com/tskit-dev/tskit/issu