code: def _find_gvcf_blocks(vcf_file, region, tmp_dir):
      
      region_file = os.path.join(tmp_dir, "cur_region.bed")
      with open(region_file, "w") as out_handle:
          chrom, coords = region.split(":")
          start, end = coords.split("-")
          out_handle.write("\t".join([chrom, start, end]) + "\n")
      final_file = os.path.join(tmp_dir, "split_regions.bed")
      cmd = "gvcf_regions.py {vcf_file} | bedtools intersect -a - -b {region_file} > {final_file}"
      do.run(cmd.format(**locals()))
      regions = []
      with open(final_file) as in_handle:
          for line in in_handle:
              chrom, start, end = line.strip().split("\t")
              regions.append("%s:%s-%s" % (chrom, start, end))
      return regions
docs: Retrieve gVCF blocks within our current evaluation region.
  
      gvcfgenotyper does not support calling larger regions with individual
      coverage blocks, so we split our big region into potentially multiple.