How to use the @angular-devkit/build-angular/src/browser.buildWebpackBrowser function in @angular-devkit/build-angular

return rxjs_1.from(setup()).pipe(operators_1.switchMap(opt => {
        return browser_1.buildWebpackBrowser(opt.buildOptions, context, {
            webpackConfiguration: util_1.electronBuildWebpackConfigTransformFactory(opt.buildOptions, opt.buildElectronOptions, context)
        });
    }), operators_1.filter((val, index) => index < 1), operators_1.tap(result => {
        // Copy electron main

switchMap(opt => {
      return buildWebpackBrowser(opt.buildOptions as any, context, {
        webpackConfiguration: electronBuildWebpackConfigTransformFactory(opt.buildOptions, opt.buildElectronOptions, context)
      });
    }),
    filter((val, index) => index < 1),

return rxjs_1.from(setup()).pipe(operators_1.switchMap(opt => {
        return browser_1.buildWebpackBrowser(opt.buildOptions, context, {
            webpackConfiguration: util_1.electronBuildWebpackConfigTransformFactory(opt.buildOptions, opt.buildElectronOptions, context)
        });
    }), operators_1.switchMap((x) => {
        count++;

switchMap(opt => {
      return buildWebpackBrowser(opt.buildOptions as any, context, {
        webpackConfiguration: electronBuildWebpackConfigTransformFactory(opt.buildOptions, opt.buildElectronOptions, context)
      });
    }),
    switchMap((x: any) => {