#if !defined(IS_MOBILE_PLATFORM)
  // Set up a multi-client distributed execution environment. Must be called on
  // all tasks in the cluster.
  // This call internally coordinates with other tasks to initialize the eager
  // context and TF server for multi-client execution.
  virtual absl::Status EnableCollectiveOps(const ServerDef& server_def) = 0;

  // Set a distributed manager that helps set up, update, and check liveness

            Currency.DOLLAR, "dollar",
            Currency.PESO, "peso",
            Currency.FRANC, "franc");
    EnumHashBiMap<Currency, String> bimap = EnumHashBiMap.create(map);

    Set<Object> uniqueEntries = Sets.newIdentityHashSet();
    uniqueEntries.addAll(bimap.entrySet());
    assertEquals(3, uniqueEntries.size());
  }

  @J2ktIncompatible
  @GwtIncompatible // serialize

```Python hl_lines="14"
{!> ../../docs_src/body_nested_models/tutorial002.py!}
```

////

## Set types

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

And Python has a special data type for sets of unique items, the `set`.

Then we can declare `tags` as a set of strings:

//// tab | Python 3.10+

```Python hl_lines="12"

func (list *TargetList) Exists(id TargetID) bool {
	list.RLock()
	defer list.RUnlock()

	_, found := list.targets[id]
	return found
}

// TargetIDResult returns result of Remove/Send operation, sets err if
// any for the associated TargetID
type TargetIDResult struct {
	// ID where the remove or send were initiated.
	ID TargetID
	// Stores any error while removing a target or while sending an event.
	Err error

	return ipList
}

func mustGetLocalLoopbacks() (ipList set.StringSet) {
	ipList = set.NewStringSet()
	for _, ip := range mustGetLocalIPs() {
		if ip != nil && ip.IsLoopback() {
			ipList.Add(ip.String())
		}
	}
	return
}

// mustGetLocalIP4 returns IPv4 addresses of localhost.  It panics on error.
func mustGetLocalIP4() (ipList set.StringSet) {
	ipList = set.NewStringSet()
	for _, ip := range mustGetLocalIPs() {

		v, ok = r.Header[xhttp.AmzContentSha256]
	}

	// Skip if no header was set.
	if !ok {
		return true
	}

	// If x-amz-content-sha256 is set and the value is not
	// 'UNSIGNED-PAYLOAD' we should validate the content sha256.
	switch v[0] {
	case unsignedPayload, unsignedPayloadTrailer:
		return true
	case emptySHA256:
		// some broken clients set empty-sha256
		// with > 0 content-length in the body,

			req.Header.Set("X-Amz-Copy-Source-If-Unmodified-Since", testCase.copyUnmodifiedHeader)
		}
		// Add custom metadata.
		for k, v := range testCase.metadata {
			req.Header.Set(k, v)
		}
		if testCase.metadataReplace {
			req.Header.Set("X-Amz-Metadata-Directive", "REPLACE")
		}
		if testCase.metadataCopy {
			req.Header.Set("X-Amz-Metadata-Directive", "COPY")
		}
		if testCase.metadataGarbage {

        if (systemProperties != null) {
            this.systemProperties = new Properties();
            // avoid concurrent modification if someone else sets/removes an unrelated system property
            synchronized (systemProperties) {
                this.systemProperties.putAll(systemProperties);
            }
        } else {
            this.systemProperties = null;

   *
   * <ul>
   *   <li>A and B have equal {@link #isDirected() directedness}.
   *   <li>A and B have equal {@link #nodes() node sets}.
   *   <li>A and B have equal {@link #edges() edge sets}.
   *   <li>The {@link #edgeValue(N, N) value} of a given edge is the same in both A and B.
   * </ul>
   *

		size: size,
	}
}

// NewBuffer returns a new RingBuffer whose buffer is provided.
func NewBuffer(b []byte) *RingBuffer {
	return &RingBuffer{
		buf:  b,
		size: len(b),
	}
}

// SetBlocking sets the blocking mode of the ring buffer.
// If block is true, Read and Write will block when there is no data to read or no space to write.
// If block is false, Read and Write will return ErrIsEmpty or ErrIsFull immediately.