How to use the @ohif/core.ExtensionManager function in @ohif/core

function _initExtensions(extensions, cornerstoneExtensionConfig, appConfig) {
  extensionManager = new ExtensionManager({
    commandsManager,
    servicesManager,
    appConfig,
  });

  const requiredExtensions = [
    GenericViewerCommands,
    [OHIFCornerstoneExtension, cornerstoneExtensionConfig],
    /* WARNING: MUST BE REGISTERED _AFTER_ OHIFCornerstoneExtension */
    MeasurementsPanel,
  ];
  const mergedExtensions = requiredExtensions.concat(extensions);
  extensionManager.registerExtensions(mergedExtensions);
}