code: def build_combined_label(sl, idxs, sep=' ', label_format=None):
      
  
      if label_format:
          return label_format % tuple([get_shortstr(str(sl[n])) for n in idxs])
      else:
          return sep.join([get_shortstr(str(sl[n])) for n in idxs])
docs: Generate a combined label from a list of indexes
      into sl, by joining them with `sep` (str).
  
      :param sl: Strings to combine
      :type sl: dict of str
      :param idxs: Indexes into sl
      :type idxs: list of sl keys
      :param sep:
  
      :return: `str` of combined label