code: def run_gvcfgenotyper(data, orig_region, vrn_files, out_file):
      
      if not utils.file_exists(out_file):
          with file_transaction(data, out_file) as tx_out_file:
              regions = _find_gvcf_blocks(vrn_files[0], bamprep.region_to_gatk(orig_region),
                                          os.path.dirname(tx_out_file))
              if len(regions) == 1:
                  _run_gvcfgenotyper(data, regions[0], vrn_files, tx_out_file)
              else:
                  split_outs = [_run_gvcfgenotyper(data, r, vrn_files,
                                                   "%s-%s.vcf.gz" % (utils.splitext_plus(out_file)[0],
                                                                     r.replace(":", "_").replace("-", "_")))
                                for r in regions]
                  vcfutils.concat_variant_files(split_outs, tx_out_file, regions,
                                                dd.get_ref_file(data), data["config"])
      return vcfutils.bgzip_and_index(out_file, data["config"])
docs: Merge strelka2 and Illumina compatible gVCFs with gvcfgenotyper.
  
      https://github.com/Illumina/gvcfgenotyper
  
      Also need to explore GLnexus (https://github.com/dnanexus-rnd/GLnexus)