code: def run_pyvcf(args):
      
      # open VCF reader
      reader = vcf.Reader(filename=args.input_vcf)
      # optionally, open VCF writer
      writer = None
      # read through input VCF file, optionally also writing out
      start = time.clock()
      num = 0
      for num, r in enumerate(reader):
          if num % 10000 == 0:
              print(num, "".join(map(str, [r.CHROM, ":", r.POS])), sep="\t", file=sys.stderr)
          if writer:
              writer.write_record(r)
          if args.max_records and num >= args.max_records:
              break
      end = time.clock()
      print("Read {} records in {} seconds".format(num, (end - start)), file=sys.stderr)
docs: Main program entry point after parsing arguments