public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().containsAll(c);
      }
    }

    @Override
    public boolean isEmpty() {
      synchronized (mutex) {
        return delegate().isEmpty();
      }
    }

    @Override
    public Iterator<E> iterator() {
      return delegate().iterator(); // manually synchronized
    }

    @Override

    public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().containsAll(c);
      }
    }

    @Override
    public boolean isEmpty() {
      synchronized (mutex) {
        return delegate().isEmpty();
      }
    }

    @Override
    public Iterator<E> iterator() {
      return delegate().iterator(); // manually synchronized
    }

    @Override

        if (parent != null) {
            String version = parent.getVersion();
            String path = Optional.ofNullable(parent.getRelativePath()).orElse("..");
            if (version == null && !path.isEmpty()) {
                Optional<RelativeProject> resolvedParent = resolveRelativePath(
                        pomFile, context, Paths.get(path), parent.getGroupId(), parent.getArtifactId());

   */
  @CanIgnoreReturnValue
  public static Set<Feature<?>> addImpliedFeatures(Set<Feature<?>> features) {
    Queue<Feature<?>> queue = new ArrayDeque<>(features);
    while (!queue.isEmpty()) {
      Feature<?> feature = queue.remove();
      for (Feature<?> implied : feature.getImpliedFeatures()) {
        if (features.add(implied)) {
          queue.add(implied);
        }
      }
    }

      throw new IllegalArgumentException(e);
    }

    boolean empty;
    if (effectiveRange.isEmpty()) {
      empty = true;
    } else {
      /*
       * requireNonNull is safe because the effectiveRange operations above would have thrown or
       * effectiveRange.isEmpty() would have returned true.
       */
      C afterLower = requireNonNull(range.lowerBound.leastValueAbove(domain));

    assertEquals(expected, CharSource.concat(ImmutableList.of(c1, c2, c3).iterator()).read());
    assertFalse(CharSource.concat(c1, c2, c3).isEmpty());

    CharSource emptyConcat = CharSource.concat(CharSource.empty(), CharSource.empty());
    assertTrue(emptyConcat.isEmpty());
  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");

  @Override
  @CheckForNull
  public V get(@CheckForNull Object key) {
    return RegularImmutableMap.get(key, keyTable, mask);
  }

  @Override
  ImmutableSet<Entry<K, V>> createEntrySet() {
    return isEmpty()
        ? ImmutableSet.<Entry<K, V>>of()
        : new ImmutableMapEntrySet.RegularEntrySet<K, V>(this, entries);
  }

  @Override
  ImmutableSet<K> createKeySet() {
    return new ImmutableMapKeySet<>(this);

        assertThat(map.size(), equalTo(4));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testIsEmpty() throws Exception {
        assertThat(map.isEmpty(), is(not(true)));
        map.clear();
        assertThat(map.isEmpty(), is(true));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testContainsValue() throws Exception {

    assertEquals(expected, CharSource.concat(ImmutableList.of(c1, c2, c3).iterator()).read());
    assertFalse(CharSource.concat(c1, c2, c3).isEmpty());

    CharSource emptyConcat = CharSource.concat(CharSource.empty(), CharSource.empty());
    assertTrue(emptyConcat.isEmpty());
  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");

        try (Stream<String> lines = Files.lines(configFile, Charset.defaultCharset())) {
            List<String> args =
                    lines.filter(arg -> !arg.isEmpty() && !arg.startsWith("#")).toList();
            O options = parseArgs("maven.config", args);
            if (options.goals().isPresent()) {
                // This file can only contain options, not args (goals or phases)