* might be absent" as two distinct types in your program, which can aid clarity.
 *
 * <p>Some uses of this class include
 *
 * <ul>
 *   <li>As a method return type, as an alternative to returning {@code null} to indicate that no
 *       value was available
 *   <li>To distinguish between "unknown" (for example, not present in a map) and "known to have no

// environment and returns a:
//
//   - connection to MinIO KMS if the "MINIO_KMS_SERVER" variable is present.
//   - connection to MinIO KES if the "MINIO_KMS_KES_ENDPOINT" is present.
//   - connection to a "local" KMS implementation using a static key if the
//     "MINIO_KMS_SECRET_KEY" or "MINIO_KMS_SECRET_KEY_FILE" is present.
//
// It returns an error if connecting to the KMS implementation fails,

  //   to allow for explanatory text as described in section 5.2 of RFC7468.
  //
  // If more than one PEM block is present, and the definition of the requested spec.signerName
  // does not indicate otherwise, the first block is the issued certificate,
  // and subsequent blocks should be treated as intermediate certificates and presented in TLS handshakes.
  //
  // The certificate is encoded in PEM format.
  //

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_unsupportedPresentExistingValue() {
    try {
      assertEquals(
          "putIfAbsent(present, existingValue) should return present or throw",
          v0(),
          getMap().putIfAbsent(k0(), v0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

        sets[i] = ImmutableSet.of();
      } else if (setSize < emptySetProportion + singletonSetProportion) {
        sets[i] = ImmutableSet.of(PRESENT);
      } else {
        sets[i] = ImmutableSet.of(PRESENT, new Object());
      }

      if (rng.nextDouble() < hitRate) {
        queries[i] = PRESENT;
      } else {
        queries[i] = ABSENT;
      }
    }
  }

  @Benchmark
  public boolean contains(int reps) {

  @CheckForNull @LazyInit private List<@Nullable Present<V>> values;

  CollectionFuture(
      ImmutableCollection<? extends ListenableFuture<? extends V>> futures,
      boolean allMustSucceed) {
    super(futures, allMustSucceed, true);

    List<@Nullable Present<V>> values =
        futures.isEmpty()
            ? Collections.<@Nullable Present<V>>emptyList()
            : Lists.<@Nullable Present<V>>newArrayListWithCapacity(futures.size());

    E duplicate = arrayAndDuplicate.duplicate;

    int firstIndex = getList().indexOf(duplicate);
    int initialSize = getList().size();
    assertTrue("remove(present) should return true", getList().remove(duplicate));
    assertTrue(
        "After remove(duplicate), a list should still contain the duplicate element",
        getList().contains(duplicate));
    assertFalse(

  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPut_unsupportedPresentExistingValue() {
    try {
      assertEquals("put(present, existingValue) should return present or throw", v0(), put(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)

  /**
   * Removes {@code node} if it is present; all edges incident to {@code node} will also be removed.
   *
   * @return {@code true} if the network was modified as a result of this call
   */
  @CanIgnoreReturnValue
  boolean removeNode(N node);

  /**
   * Removes {@code edge} from this network, if it is present.
   *

  /**
   * Adds {@code node} if it is not already present.
   *
   * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null.
   *
   * @return {@code true} if the graph was modified as a result of this call
   */
  @CanIgnoreReturnValue
  boolean addNode(N node);

  /**
   * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present, and sets