2D Plot Node Template: Unions are not allowed in return type

[rowandempster]

Copying directly from the given template:

import { Input, Messages } from "ros";
import { TwoDimensionalPlot, TwoDimensionalPlotLine } from "./types";

type GlobalVariables = { id: number };

export const inputs = ["/mpc_stats"];
export const output = "/webviz_node/";

// Populate 'Input' with a parameter to properly type your inputs, e.g. 'Input<"/your_input_topic">'
const publisher = (
  message: Input<"/mpc_stats">,
  globalVars: GlobalVariables
): TwoDimensionalPlot => {
  const lines: TwoDimensionalPlotLine[] = [];
  const points: TwoDimensionalPlotLine[] = [];
  const polygons: TwoDimensionalPlotLine[] = [];

  return {
    lines,
    points,
    polygons
  };
};

export default publisher;

Gives the TS compilation error Unions are not allowed in return type.DatatypeExtraction

TwoDimensionalPlot contains the union PointStyle, is this the issue?