docs: @BetaApi
    public final Operation resizeRegionInstanceGroupManager(
        Integer size, ProjectRegionInstanceGroupManagerName instanceGroupManager) {
  
      ResizeRegionInstanceGroupManagerHttpRequest request =
          ResizeRegionInstanceGroupManagerHttpRequest.newBuilder()
              .setSize(size)
              .setInstanceGroupManager(
                  instanceGroupManager == null ? null : instanceGroupManager.toString())
              .build();
      return resizeRegionInstanceGroupManager(request);
    }