code: def _pack_cwl(unpacked_cwl):
      
      out_file = "%s-pack%s" % os.path.splitext(unpacked_cwl)
      cmd = "cwltool --pack {unpacked_cwl} > {out_file}"
      _run_tool(cmd.format(**locals()))
      return out_file
docs: Pack CWL into a single document for submission.