code: function sectionBounds(token) {
      var start = token[3];
      var end = start;
  
      var tokens;
      while ((tokens = token[4]) && tokens.length) {
        token = tokens[tokens.length - 1];
        end = token[3];
      }
  
      return [start, end];
    }
docs: Calculates the bounds of the section represented by the given `token` in
  the original template by drilling down into nested sections to find the
  last token that is part of that section. Returns an array of [start, end].