code: @BetaApi
    public final Operation deleteRegionInstanceGroupManager(String instanceGroupManager) {
  
      DeleteRegionInstanceGroupManagerHttpRequest request =
          DeleteRegionInstanceGroupManagerHttpRequest.newBuilder()
              .setInstanceGroupManager(instanceGroupManager)
              .build();
      return deleteRegionInstanceGroupManager(request);
    }
docs: Deletes the specified managed instance group and all of the instances in that group.
  
  <p>Sample code:
  
  <pre><code>
  try (RegionInstanceGroupManagerClient regionInstanceGroupManagerClient = RegionInstanceGroupManagerClient.create()) {
  ProjectRegionInstanceGroupManagerName instanceGroupManager = ProjectRegionInstanceGroupManagerName.of("[PROJECT]", "[REGION]", "[INSTANCE_GROUP_MANAGER]");
  Operation response = regionInstanceGroupManagerClient.deleteRegionInstanceGroupManager(instanceGroupManager.toString());
  }
  </code></pre>
  
  @param instanceGroupManager Name of the managed instance group to delete.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails