code: func resourceVSphereComputeClusterVMAntiAffinityRuleFlattenID(cluster *object.ClusterComputeResource, key int32) (string, error) {
  	clusterID := cluster.Reference().Value
  	return strings.Join([]string{clusterID, strconv.Itoa(int(key))}, ":"), nil
  }
docs: // resourceVSphereComputeClusterVMAntiAffinityRuleFlattenID makes an ID for the
  // vsphere_compute_cluster_vm_anti_affinity_rule resource.