code: def setup_multiifo_combine_statmap(workflow, final_bg_file_list, out_dir, tags):
      
      if tags is None:
          tags = []
      make_analysis_dir(out_dir)
      logging.info('Setting up multiifo combine statmap')
  
      cstat_exe = PyCBCMultiifoCombineStatmap(workflow.cp,
                                              'combine_statmap',
                                              ifos=workflow.ifos,
                                              tags=tags,
                                              out_dir=out_dir)
  
      ifolist = ' '.join(workflow.ifos)
      cluster_window = float(workflow.cp.get_opt_tags('combine_statmap',
                                                      'cluster-window',
                                                      tags))
      combine_statmap_node = cstat_exe.create_node(final_bg_file_list,
                                                   ifolist,
                                                   cluster_window,
                                                   tags)
      workflow.add_node(combine_statmap_node)
      return combine_statmap_node.output_file
docs: Combine the multiifo statmap files into one background file