How to use the vega-dataflow.changeset function in vega-dataflow

this._renderer = null;
  this._handler = new CanvasHandler().scene(root);
  this._queue = null;
  this._eventListeners = [];

  // initialize dataflow graph
  var ctx = runtime(this, spec);
  this._signals = ctx.signals;
  this._data = ctx.data;

  // initialize scenegraph
  if (ctx.root) ctx.root.set(root);
  this.pulse(
    this._data.root.input,
    changeset().insert(root.items)
  );

  // background color
  this._backgroundColor = null;

  // initialize resize operator
  this.add(null,
    function(_, pulse) { pulse.dataflow.resize(_.width, _.height); },
    {width: this._signals.width, height: this._signals.height}
  );
}

function pushData(data: any[], pipeline: Pipeline) {
	const { dataflow, start } = pipeline
	dataflow.pulse(start, changeset().insert(data)).run()
}

export function insert(name, _) {
  return change.call(this, name, changeset().insert(_));
}

export function remove(name, _) {
  return change.call(this, name, changeset().remove(_));
}