getNodeData(nodeId) {

    const data = $tw.wiki.getCacheForTiddler(this.mapTRef, "tmap-map", () => utils.parseFieldData(this.mapTRef, 'text', {}));

    return (nodeId ? data[nodeId] : data);

  }
This method will return the node data stored in the view.

@todo When to delete obsolete data?

@param {string} nodeId
@result {Hashmap<Id, Object>} A Hashmap with node data.