* {@code profile > project}, hence active profile property may override project property.
     * <p>
     * The caller of this method should decide whether there is a project in scope (hence, a project instance
     * needs to be passed) or not.
     *
     * @param project {@link Project} or {@code null}.
     * @return the effective properties, never {@code null}
     */
    @Nonnull

   * the two sets. If you have reason to believe one of your sets will generally be smaller than the
   * other, pass it first. Unfortunately, since this method sets the generic type of the returned
   * set based on the type of the first set passed, this could in rare cases force you to make a
   * cast, for example:
   *
   * <pre>{@code
   * Set<Object> aFewBadObjects = ...
   * Set<String> manyBadStrings = ...
   *

   * IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code fromKey}.
   * However, this method doesn't throw an exception in that situation, but instead keeps the
   * original {@code fromKey}. Similarly, this method keeps the original {@code toKey}, instead of
   * throwing an exception, if passed a {@code toKey} greater than an earlier {@code toKey}.
   */
  @Override

   * ImmutableMapValues<K, V>(this)}, but ProGuard can't figure out how to eliminate that default
   * when RegularImmutableMap overrides it.
   */
  abstract ImmutableCollection<V> createValues();

  // cached so that this.multimapView().inverse() only computes inverse once
  @LazyInit @CheckForNull private transient ImmutableSetMultimap<K, V> multimapView;

  /**
   * Returns a multimap view of the map.
   *

    Iterator<String> itr2 = Iterators.concat(itr1, singletonIterator("d"));
    assertEquals("c", itr2.next());
    assertEquals("d", itr2.next());
  }

  /** Illustrates the somewhat bizarre behavior when a null is passed in. */
  public void testConcatContainingNull() {
    Iterator<Iterator<Integer>> input =
        (Iterator<Iterator<Integer>>)
            Arrays.<@Nullable Iterator<Integer>>asList(iterateOver(1, 2), null, iterateOver(3))