func TestDoesV4PresignParamsExist(t *testing.T) {
	testCases := []struct {
		inputQueryKeyVals []string
		expectedErrCode   APIErrorCode
	}{
		// Test case - 1.
		// contains all query param keys which are necessary for v4 presign request.
		{
			inputQueryKeyVals: []string{
				"X-Amz-Algorithm", "",
				"X-Amz-Credential", "",
				"X-Amz-Signature", "",
				"X-Amz-Date", "",

    resetContainer(mapEntry(k0(), v0()), mapEntry(k0(), v1()), mapEntry(k1(), v0()));
    Multiset<K> keys = multimap().keys();
    assertEquals(2, keys.count(k0()));
    assertEquals(1, keys.count(k1()));
    assertEquals(3, keys.size());
    assertContainsAllOf(keys, k0(), k1());
    assertContainsAllOf(
        keys.entrySet(), Multisets.immutableEntry(k0(), 2), Multisets.immutableEntry(k1(), 1));
  }

    resetContainer(mapEntry(k0(), v0()), mapEntry(k0(), v1()), mapEntry(k1(), v0()));
    Multiset<K> keys = multimap().keys();
    assertEquals(2, keys.count(k0()));
    assertEquals(1, keys.count(k1()));
    assertEquals(3, keys.size());
    assertContainsAllOf(keys, k0(), k1());
    assertContainsAllOf(
        keys.entrySet(), Multisets.immutableEntry(k0(), 2), Multisets.immutableEntry(k1(), 1));
  }

We can do better...

## What makes a dependency { #what-makes-a-dependency }

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

    /** The key of the message: </ul> */
    public static final String ERRORS_FOOTER = "{errors.footer}";

    /** The key of the message: <li><i class="fa fa-exclamation-circle"></i> */
    public static final String ERRORS_PREFIX = "{errors.prefix}";

    /** The key of the message: </li> */
    public static final String ERRORS_SUFFIX = "{errors.suffix}";

    /** The key of the message: {item} must be false. */

    public static final String LABELS_FACET = "{labels.facet}";

    /** The key of the message: Geo */
    public static final String LABELS_GEO = "{labels.geo}";

    /** The key of the message: Groups */
    public static final String LABELS_GROUPS = "{labels.groups}";

    /** The key of the message: Hash */
    public static final String LABELS_HASH = "{labels.hash}";

    E[] keys = clazz.getEnumConstants();
    int numKeys = keys.length;
    ArrayList<LockGraphNode> nodes = Lists.newArrayListWithCapacity(numKeys);
    // Create a LockGraphNode for each enum value.
    for (E key : keys) {
      LockGraphNode node = new LockGraphNode(getLockName(key));
      nodes.add(node);
      map.put(key, node);
    }

	if err != nil {
		etcdLogOnceIf(ctx, err, "etcd-retrieve-keys")
		return nil, etcdErrToErr(err, client.Endpoints())
	}
	if resp.Count == 0 {
		return nil, errConfigNotFound
	}
	for _, ev := range resp.Kvs {
		if string(ev.Key) == key {
			return ev.Value, nil
		}
	}
	return nil, errConfigNotFound

   * over keys in the order they were first encountered in the input, and the values for each key
   * are iterated in the order they were encountered. If two values for the same key are {@linkplain
   * Object#equals equal}, the first value encountered is used.
   *
   * @throws NullPointerException if any key, value, or entry is null
   * @since 19.0
   */

// while reading the object from another source.
// Notice: The S3 client can send secret keys in headers for encryption related jobs,
// the handler should ensure to remove these keys before sending them to the object layer.
// Currently these keys are:
//   - X-Amz-Server-Side-Encryption-Customer-Key
//   - X-Amz-Copy-Source-Server-Side-Encryption-Customer-Key
func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Request) {