code: def _prepare_cwl_tarballs(data_dir):
      
      for dbref_dir in filter(os.path.isdir, glob.glob(os.path.join(data_dir, "genomes", "*", "*"))):
          base_dir, dbref = os.path.split(dbref_dir)
          for indexdir in TARBALL_DIRECTORIES:
              cur_target = os.path.join(dbref_dir, indexdir)
              if os.path.isdir(cur_target):
                  # Some indices, like rtg, have a single nested directory
                  subdirs = [x for x in os.listdir(cur_target) if os.path.isdir(os.path.join(cur_target, x))]
                  if len(subdirs) == 1:
                      cur_target = os.path.join(cur_target, subdirs[0])
                  create.directory_tarball(cur_target)
docs: Create CWL ready tarballs for complex directories.
  
      Avoids need for CWL runners to pass and serialize complex directories
      of files, which is inconsistent between runners.