docs: def dots_to_empty_cells(config, tsv_fpath):
      """Put dots instead of empty cells in order to view TSV with column -t
      """
      def proc_line(l, i):
          while '\t\t' in l:
              l = l.replace('\t\t', '\t.\t')
          return l
      return iterate_file(config, tsv_fpath, proc_line, suffix='dots')