code: def _append_trivial_tree(self, text_file, sync_root):
          
          interval = sync_root.value
          #
          # NOTE the following is correct, but it is a bit obscure
          # time_values = [interval.begin] * (1 + len(text_file)) + [interval.end] * 2
          #
          if len(text_file) == 1:
              time_values = [interval.begin, interval.begin, interval.end, interval.end]
          else:
              # interval.begin == interval.end
              time_values = [interval.begin] * (3 + len(text_file))
          aba = AdjustBoundaryAlgorithm(rconf=self.rconf, logger=self.logger)
          aba.intervals_to_fragment_list(
              text_file=text_file,
              time_values=time_values
          )
          aba.append_fragment_list_to_sync_root(sync_root=sync_root)
docs: Append trivial tree, made by one HEAD,
          one sync map fragment for each element of ``text_file``,
          and one TAIL.
  
          This function is called if either ``text_file`` has only one element,
          or if ``sync_root.value`` is an interval with zero length
          (i.e., ``sync_root.value.begin == sync_root.value.end``).