return new Present<>(
        checkNotNull(
            function.apply(reference),
            "the Function passed to Optional.transform() must not return null."));
  }

  @Override
  public boolean equals(@CheckForNull Object object) {
    if (object instanceof Present) {
      Present<?> other = (Present<?>) object;
      return reference.equals(other.reference);
    }

    return new Present<>(
        checkNotNull(
            function.apply(reference),
            "the Function passed to Optional.transform() must not return null."));
  }

  @Override
  public boolean equals(@CheckForNull Object object) {
    if (object instanceof Present) {
      Present<?> other = (Present<?>) object;
      return reference.equals(other.reference);
    }

  /**
   * 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

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemove_present() {
    int initialSize = collection.size();
    assertTrue("remove(present) should return true", collection.remove(e0()));
    assertEquals(
        "remove(present) should decrease a collection's size by one.",
        initialSize - 1,
        collection.size());
    expectMissing(e0());
  }

    switch (presentBehavior) {
      case FIRST_PRESENT:
        if (list.contains(key)) {
          assertEquals(list.indexOf(key), answer);
          return;
        }
        break;
      case LAST_PRESENT:
        if (list.contains(key)) {
          assertEquals(list.lastIndexOf(key), answer);
          return;
        }
        break;
      case ANY_PRESENT:
        if (list.contains(key)) {

    // flip GOLDEN_PRESENT_KEY to true even if it wasn't explicitly inserted
    // (false positive).
    assertThat(bloomFilter.mightContain(GOLDEN_PRESENT_KEY)).isFalse();
    for (int i = 0; i < NUM_PUTS; i++) {
      bloomFilter.put(getNonGoldenRandomKey());
    }
    bloomFilter.put(GOLDEN_PRESENT_KEY);

    int numThreads = 12;

public class SetRemoveTester<E> extends AbstractSetTester<E> {
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemove_present() {
    getSet().remove(e0());
    assertFalse(
        "After remove(present) a set should not contain the removed element.",
        getSet().contains(e0()));
  }

public class MultisetSetCountConditionallyTester<E> extends AbstractMultisetSetCountTester<E> {
  @Override
  void setCountCheckReturnValue(E element, int count) {
    assertTrue(
        "setCount() with the correct expected present count should return true",
        setCount(element, count));
  }

  @Override
  void setCountNoCheckReturnValue(E element, int count) {
    setCount(element, count);
  }

  @CanIgnoreReturnValue

  /**
   * 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.
   *

  }

  @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)