How to use the vega-dataflow/src/Tuple.set function in vega-dataflow

prototype.batchTransform = function(input, data) {
  log.debug(input, ['voronoi']);

  // get variables
  var pathname = this._output.path;

  // configure layout
  var polygons = this._layout
    .clipExtent(this.param('clipExtent'))
    .x(this.param('x').accessor)
    .y(this.param('y').accessor)
    (data);

  // build and assign path strings
  for (var i=0; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i

.on('end', function(words) {
      var size = layout.size(),
          dx = size[0] >> 1,
          dy = size[1] >> 1,
          w, t, i, len;

      for (i=0, len=words.length; i