/**
   * Returns a builder that creates immutable sorted maps whose keys are ordered by their natural
   * ordering. The sorted maps use {@link Ordering#natural()} as the comparator.
   */
  public static <K extends Comparable<?>, V> Builder<K, V> naturalOrder() {
    return new Builder<>(Ordering.natural());
  }

  /**
   * Returns a builder that creates immutable sorted maps with an explicit comparator. If the

  /**
   * Returns a builder that creates immutable sorted maps whose keys are ordered by their natural
   * ordering. The sorted maps use {@link Ordering#natural()} as the comparator.
   */
  public static <K extends Comparable<?>, V> Builder<K, V> naturalOrder() {
    return new Builder<>(Ordering.natural());
  }

  /**
   * Returns a builder that creates immutable sorted maps with an explicit comparator. If the

    SortedMapDifference<Integer, Integer> diff = Maps.difference(SORTED_EMPTY, SORTED_EMPTY);
    assertTrue(diff.areEqual());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnLeft());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnRight());
    assertEquals(SORTED_EMPTY, diff.entriesInCommon());
    assertEquals(SORTED_EMPTY, diff.entriesDiffering());
    assertEquals("equal", diff.toString());
  }

    SortedMapDifference<Integer, Integer> diff = Maps.difference(SORTED_EMPTY, SORTED_EMPTY);
    assertTrue(diff.areEqual());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnLeft());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnRight());
    assertEquals(SORTED_EMPTY, diff.entriesInCommon());
    assertEquals(SORTED_EMPTY, diff.entriesDiffering());
    assertEquals("equal", diff.toString());
  }

      int expectedSize) {
    return new LinkedHashSet<>(Maps.capacity(expectedSize));
  }

  // TreeSet

  /**
   * Creates a <i>mutable</i>, empty {@code TreeSet} instance sorted by the natural sort ordering of
   * its elements.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link ImmutableSortedSet#of()} instead.
   *

   * weak, or phantom references.
   *
   * @param map place to store the mapping from each key to its corresponding values
   * @param factory supplier of new, empty sorted sets that will each hold all values for a given
   *     key
   * @throws IllegalArgumentException if {@code map} is not empty
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>

  }

  /**
   * An iterator that performs a lazy N-way merge, calculating the next value each time the iterator
   * is polled. This amortizes the sorting cost over the iteration and requires less memory than
   * sorting all elements at once.
   *
   * <p>Retrieving a single element takes approximately O(log(M)) time, where M is the number of

  }

  /**
   * An iterator that performs a lazy N-way merge, calculating the next value each time the iterator
   * is polled. This amortizes the sorting cost over the iteration and requires less memory than
   * sorting all elements at once.
   *
   * <p>Retrieving a single element takes approximately O(log(M)) time, where M is the number of