How to use the vega.config function in vega

const express = require('express');
const vg = require('vega');

vg.config.load.baseURL = 'https://vega.github.io/vega-editor/app/';

const TYPES = {
  VegaLite: require('./charts/VegaLite'),
  Bar: require('./charts/Bar'),
  DistrictBar: require('./charts/DistrictBar'),
  DemographicBar: require('./charts/DemographicBar'),
  ZurichMap: require('./charts/ZurichMap')
};

const app = express();
app.get('/:type', (request, response) => {
  if (!TYPES[request.params.type]) {
    return response.status(404).send('Not Found');
  }

  const spec = TYPES[request.params.type]({

'use strict';

var vgCfg = require('vega').config,
    axisDef = vgCfg.axis,
    legendDef = vgCfg.legend,
    GTYPES = {AXIS: 'axis', LEGEND: 'legend'},
    ORIENT = {x: 'bottom', y: 'left'};

/**
 * A factory to produce a Lyra guide (axis or legend).
 *
 * @param {number} gtype - Axis or Legend (use enumerated `Guide.TYPES`).
 * @param {string} type - Axis/legend type (e.g., `x` axis, or `fill` legend).
 * @param {number|Object} scale - The ID or Lyra Scale Primitive that backs the guide.
 *
 * @property {number} _gtype - Axis or Legend (based on enumerate `Guide.TYPES`).
 * @property {string} _type - Type for legends (e.g., `fill`, `stroke`, etc.).
 * @see Vega's {@link https://github.com/vega/vega/wiki/Axes|Axes} or
 * {@link https://github.com/vega/vega/wiki/Legends|Legends} documentation for