%instance_key = "tf.Const"() { value = dense<3> : tensor<i32> } : () -> tensor<i32>
  // CHECK: %[[REDUCE:.*]] = "mhlo.all_reduce"
  // CHECK-SAME{LITERAL}: replica_groups = dense<[[0, 1]]> : tensor<1x2xi64>
  // CHECK: mhlo.add
  // CHECK: mhlo.return
  // CHECK: return %[[REDUCE]]

  Pattern<
    (TF_CollectiveReduceV2Op:$src_op
       $input, $group_size, $group_key, $instance_key, $ordering_token,
       $merge_op, $final_op, $communication_hint, $timeout_seconds,
       $is_stateless, $max_subdivs_per_device
    ),
    [(TF_CollectiveReduceV2Op
       $input, $group_size, $group_key, $instance_key, (EmptyList),
       $merge_op, $final_op, $communication_hint, $timeout_seconds,

  TF_DeleteStatus(status);

  TFE_OpSetAttrType(op, "T", TFE_TensorHandleDataType(in));
  TFE_OpSetAttrInt(op, "group_size", group_size);
  TFE_OpSetAttrInt(op, "group_key", 123);
  TFE_OpSetAttrInt(op, "instance_key", 456);
  TFE_OpSetAttrString(op, "merge_op", "Add", 3);
  TFE_OpSetAttrString(op, "final_op", "Id", 2);
  std::vector<int64_t> subdiv_offsets;
  TFE_OpSetAttrIntList(op, "subdiv_offsets", subdiv_offsets.data(),

)

// instancesKey acts as a key to identify all instances for a given hostname/namespace pair
// This is mostly used as an index
type instancesKey struct {
	hostname  host.Name
	namespace string
}

type octetPair struct {
	thirdOctet  int
	fourthOctet int
}

func makeInstanceKey(i *model.ServiceInstance) instancesKey {
	return instancesKey{i.Service.Hostname, i.Service.Attributes.Namespace}

	}
	expected := map[string]struct{}{}
	for _, i := range want {
		expected[instanceKey(i)] = struct{}{}
	}
	unexpected := map[string]struct{}{}
	for _, i := range all {
		k := instanceKey(i)
		if _, ok := expected[k]; !ok {
			unexpected[k] = struct{}{}
		}
	}
	for _, i := range got {
		k := instanceKey(i)
		// just remove the items rather than looping over expected, if anythings left we missed it