Set<K> keySet = new HashSet<>();
      List<Entry<K, V>> builder = new ArrayList<>();
      for (Object o : elements) {
        Entry<?, ?> entry = (Entry<?, ?>) o;
        // These come from Entry<K, Collection<V>>> objects somewhere.
        @SuppressWarnings("unchecked")
        K key = (K) entry.getKey();
        keySet.add(key);

     *
     * @param cmdList the command list to add properties to
     */
    protected void addFessConfigProperties(final List<String> cmdList) {
        System.getProperties()
                .keySet()
                .stream()
                .filter(k -> k != null && k.toString().startsWith(Constants.FESS_CONFIG_PREFIX))
                .forEach(k -> addSystemProperty(cmdList, k.toString(), null, null));
    }

    Multimap<String, Integer> map = create();
    map.put("bar", 1);
    map.put("foo", 2);
    map.put("bar", 3);
    map.put("bar", 4);
    assertEquals("[bar, foo]", map.keySet().toString());
    map.keySet().remove("bar");
    assertEquals("{foo=[2]}", map.toString());
  }

  public void testLinkedKeys() {
    Multimap<String, Integer> map = create();
    map.put("bar", 1);
    map.put("foo", 2);

    }

    /**
     * Returns a Set view of the keys contained in this map.
     *
     * @return a set view of the keys contained in this map
     */
    @Override
    public Set<String> keySet() {
        return parent.keySet();
    }

    /**
     * Returns a Collection view of the values contained in this map.
     *
     * @return a collection view of the values contained in this map
     */
    @Override

    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public Set<K> keySet() {
      /*
       * We can't use StandardKeySet, as NavigableMapTestSuiteBuilder assumes that our keySet is a
       * NavigableSet. We test StandardKeySet in the superclass, so it's still covered.
       */
      return navigableKeySet();
    }

    @Override

            .build();

    ImmutableMap<Range<Integer>, Integer> test = nonEmptyRangeMap.asMapOfRanges();

    for (Range<Integer> range : test.keySet()) {
      SerializableTester.reserializeAndAssert(range);
    }

    SerializableTester.reserializeAndAssert(test.keySet());

    SerializableTester.reserializeAndAssert(nonEmptyRangeMap);
  }

    @Override
    public int size() {
      return ImmutableMap.this.size();
    }

    @Override
    public ImmutableSet<K> keySet() {
      return ImmutableMap.this.keySet();
    }

    @Override
    public boolean containsKey(@Nullable Object key) {
      return ImmutableMap.this.containsKey(key);
    }

    @Override

    // Each of the values added to the map should either still be there, or have seen a removal
    // notification.
    assertEquals(expectedKeys, Sets.union(cache.asMap().keySet(), removalNotifications.keySet()));
    assertTrue(Sets.intersection(cache.asMap().keySet(), removalNotifications.keySet()).isEmpty());
    threadPool.shutdown();
    threadPool.awaitTermination(300, SECONDS);
  }

  /**

    // Each of the values added to the map should either still be there, or have seen a removal
    // notification.
    assertEquals(expectedKeys, Sets.union(cache.asMap().keySet(), removalNotifications.keySet()));
    assertTrue(Sets.intersection(cache.asMap().keySet(), removalNotifications.keySet()).isEmpty());
    threadPool.shutdown();
    threadPool.awaitTermination(300, SECONDS);
  }

  /**

  public void testSameComparator() {
    assertTrue(SortedIterables.hasSameComparator(Ordering.natural(), Sets.newTreeSet()));
    assertTrue(SortedIterables.hasSameComparator(Ordering.natural(), Maps.newTreeMap().keySet()));
    assertTrue(
        SortedIterables.hasSameComparator(
            Ordering.natural().reverse(), Sets.newTreeSet(Ordering.natural().reverse())));
  }

  public void testComparator() {