code: def to_standardonly(in_file, ref_file, data):
      
      from bcbio.heterogeneity import chromhacks
      out_file = "%s-stdchrs.vcf.gz" % utils.splitext_plus(in_file)[0]
      if not utils.file_exists(out_file):
          stds = []
          for c in ref.file_contigs(ref_file):
              if chromhacks.is_nonalt(c.name):
                  stds.append(c.name)
          if stds:
              with file_transaction(data, out_file) as tx_out_file:
                  stds = ",".join(stds)
                  in_file = bgzip_and_index(in_file, data["config"])
                  cmd = "bcftools view -o {tx_out_file} -O z {in_file} {stds}"
                  do.run(cmd.format(**locals()), "Subset to standard chromosomes")
      return bgzip_and_index(out_file, data["config"]) if utils.file_exists(out_file) else in_file
docs: Subset a VCF input file to standard chromosomes (1-22,X,Y,MT).