code: @BetaApi
    public final Operation insertInstanceGroupManager(
        String zone, InstanceGroupManager instanceGroupManagerResource) {
  
      InsertInstanceGroupManagerHttpRequest request =
          InsertInstanceGroupManagerHttpRequest.newBuilder()
              .setZone(zone)
              .setInstanceGroupManagerResource(instanceGroupManagerResource)
              .build();
      return insertInstanceGroupManager(request);
    }
docs: Creates a managed instance group using the information that you specify in the request. After
  the group is created, instances in the group are created using the specified instance template.
  This operation is marked as DONE when the group is created even if the instances in the group
  have not yet been created. You must separately verify the status of the individual instances
  with the listmanagedinstances method.
  
  <p>A managed instance group can have up to 1000 VM instances per group. Please contact Cloud
  Support if you need an increase in this limit.
  
  <p>Sample code:
  
  <pre><code>
  try (InstanceGroupManagerClient instanceGroupManagerClient = InstanceGroupManagerClient.create()) {
  ProjectZoneName zone = ProjectZoneName.of("[PROJECT]", "[ZONE]");
  InstanceGroupManager instanceGroupManagerResource = InstanceGroupManager.newBuilder().build();
  Operation response = instanceGroupManagerClient.insertInstanceGroupManager(zone.toString(), instanceGroupManagerResource);
  }
  </code></pre>
  
  @param zone The name of the zone where you want to create the managed instance group.
  @param instanceGroupManagerResource An Instance Group Manager resource. (== resource_for
  beta.instanceGroupManagers ==) (== resource_for v1.instanceGroupManagers ==) (==
  resource_for beta.regionInstanceGroupManagers ==) (== resource_for
  v1.regionInstanceGroupManagers ==)
  @throws com.google.api.gax.rpc.ApiException if the remote call fails