Method headSet

guava/src/com/google/common/collect/Maps.java:4051–4054

(@ParametricNullness K toElement, boolean inclusive)

    }

    @Override
    public NavigableSet<K> headSet(@ParametricNullness K toElement, boolean inclusive) {
      return map().headMap(toElement, inclusive).navigableKeySet();
    }

    @Override
    public SortedSet<K> headSet(@ParametricNullness K toElement) {