code: def group(args):
      
      p = OptionParser(group.__doc__)
      p.set_outfile()
  
      opts, args = p.parse_args(args)
  
      if len(args) < 1:
          sys.exit(not p.print_help())
  
      anchorfiles = args
      groups = Grouper()
      for anchorfile in anchorfiles:
          ac = AnchorFile(anchorfile)
          for a, b, idx in ac.iter_pairs():
              groups.join(a, b)
  
      logging.debug("Created {0} groups with {1} members.".\
                    format(len(groups), groups.num_members))
  
      outfile = opts.outfile
      fw = must_open(outfile, "w")
      for g in groups:
          print(",".join(sorted(g)), file=fw)
      fw.close()
  
      return outfile
docs: %prog group anchorfiles
  
      Group the anchors into ortho-groups. Can input multiple anchor files.