public void remove() {
      checkRemove(lastReturned != null);
      MapMakerInternalMap.this.remove(lastReturned.getKey());
      lastReturned = null;
    }
  }

  final class KeyIterator extends HashIterator<K> {

    @Override
    public K next() {
      return nextEntry().getKey();
    }
  }

  final class ValueIterator extends HashIterator<V> {

    @Override

    public void remove() {
      checkRemove(lastReturned != null);
      MapMakerInternalMap.this.remove(lastReturned.getKey());
      lastReturned = null;
    }
  }

  final class KeyIterator extends HashIterator<K> {

    @Override
    public K next() {
      return nextEntry().getKey();
    }
  }

  final class ValueIterator extends HashIterator<V> {

    @Override

                        null,
                        "version of a plugin must be defined. ",
                        plugin);
            }

            String key = plugin.getKey();

            Plugin existing = index.get(key);

            if (existing != null) {
                addViolation(
                        problems,
                        errOn31,

                        null,
                        "version of a plugin must be defined. ",
                        plugin);
            }

            String key = plugin.getKey();

            Plugin existing = index.get(key);

            if (existing != null) {
                addViolation(
                        problems,
                        errOn31,

                requireNonNull(e2);
                return comparator.compare(e1.getKey(), e2.getKey());
              });
          // requireNonNull is safe because the first `size` elements have been filled in.
          Entry<K, V> firstEntry = requireNonNull(entryArray[0]);
          K prevKey = firstEntry.getKey();
          keys[0] = prevKey;
          values[0] = firstEntry.getValue();

    assertEquals("Hello", entry.getKey());
    assertEquals("World", entry.getValue());
    assertTrue(iter.hasNext());

    entry = iter.next();
    assertEquals("first", entry.getKey());
    assertEquals("second", entry.getValue());
    assertTrue(iter.hasNext());

    entry = iter.next();
    assertEquals("polygene", entry.getKey());
    assertEquals("lubricants", entry.getValue());

            Model model = lineage.get(i);
            Build build = model.getBuild();
            if (build != null) {
                for (Plugin plugin : build.getPlugins()) {
                    String key = plugin.getKey();
                    if (versions.get(key) == null) {
                        versions.put(key, plugin.getVersion());
                        plugins.put(key, plugin);
                    }
                }

            Model model = lineage.get(i);
            Build build = model.getBuild();
            if (build != null) {
                for (Plugin plugin : build.getPlugins()) {
                    String key = plugin.getKey();
                    if (versions.get(key) == null) {
                        versions.put(key, plugin.getVersion());
                        plugins.put(key, plugin);
                    }
                }

        return multimap().containsEntry(entry.getKey(), entry.getValue());
      }
      return false;
    }

    @Override
    public boolean remove(@CheckForNull Object o) {
      if (o instanceof Map.Entry) {
        Map.Entry<?, ?> entry = (Map.Entry<?, ?>) o;
        return multimap().remove(entry.getKey(), entry.getValue());
      }
      return false;
    }

        if (properties != null && !properties.isEmpty()) {
            return properties.entrySet().stream()
                    .collect(Collectors.toMap(e -> String.valueOf(e.getKey()), e -> String.valueOf(e.getValue())));

        } else {
            return null;
        }
    }

    @SuppressWarnings("unchecked")