if (length == size()) {
      return this;
    } else if (length == 0) {
      return of();
    } else {
      return subListUnchecked(fromIndex, toIndex);
    }
  }

  /**
   * Called by the default implementation of {@link #subList} when {@code toIndex - fromIndex > 1},
   * after index validation has already been performed.
   */
  ImmutableList<E> subListUnchecked(int fromIndex, int toIndex) {

   * Returns a new builder, expecting the specified number of distinct elements to be added.
   *
   * <p>If {@code expectedSize} is exactly the number of distinct elements added to the builder
   * before {@link Builder#build} is called, the builder is likely to perform better than an unsized
   * {@link #builder()} would have.
   *
   * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,

     * subclass overrides all the methods that access it here. Thus, all the methods here can safely
     * assume that this field is non-null.
     */
    @CheckForNull ObjectCountHashMap<E> contents;

    /**
     * If build() has been called on the current contents multiset, we need to copy it on any future
     * modifications, or we'll modify the already-built ImmutableMultiset.
     */

    }

    @Override
    public Set<K> elementSet() {
      return multimap.keySet();
    }

    @Override
    Iterator<K> elementIterator() {
      throw new AssertionError("should never be called");
    }
  }

  /** A skeleton implementation of {@link Multimap#entries()}. */
  abstract static class Entries<K extends @Nullable Object, V extends @Nullable Object>

   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is not type-safe, as it may be called on elements that are not mutually
   * comparable.
   *
   * @throws ClassCastException if the elements are not mutually comparable
   * @throws NullPointerException if any of {@code elements} is null
   */

  /**
   * Returns an iterator that cycles indefinitely over the elements of {@code iterable}.
   *
   * <p>The returned iterator supports {@code remove()} if the provided iterator does. After {@code
   * remove()} is called, subsequent cycles omit the removed element, which is no longer in {@code
   * iterable}. The iterator's {@code hasNext()} method returns {@code true} until {@code iterable}
   * is empty.
   *