code: def merge_perchrom_vcfs(job, perchrom_vcfs, tool_name, univ_options):
      
      work_dir = os.getcwd()
      input_files = {''.join([chrom, '.vcf']): jsid for chrom, jsid in perchrom_vcfs.items()}
      input_files = get_files_from_filestore(job, input_files, work_dir, docker=False)
      first = True
      with open(''.join([work_dir, '/', 'all_merged.vcf']), 'w') as outvcf:
          for chromvcfname in chrom_sorted([x.rstrip('.vcf') for x in input_files.keys()]):
              with open(input_files[chromvcfname + '.vcf'], 'r') as infile:
                  for line in infile:
                      line = line.strip()
                      if line.startswith('#'):
                          if first:
                              print(line, file=outvcf)
                          continue
                      first = False
                      print(line, file=outvcf)
      output_file = job.fileStore.writeGlobalFile(outvcf.name)
      export_results(job, output_file, outvcf.name, univ_options, subfolder='mutations/' + tool_name)
      job.fileStore.logToMaster('Ran merge_perchrom_vcfs for %s successfully' % tool_name)
      return output_file
docs: Merge per-chromosome vcf files into a single genome level vcf.
  
      :param dict perchrom_vcfs: Dictionary with chromosome name as key and fsID of the corresponding
             vcf as value
      :param str tool_name: Name of the tool that generated the vcfs
      :returns: fsID for the merged vcf
      :rtype: toil.fileStore.FileID