@Override
    public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
      return filter(unfiltered().headSet(toElement, inclusive), predicate);
    }

    @Override
    public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
      return filter(unfiltered().tailSet(fromElement, inclusive), predicate);
    }
  }

  /**

        return delegate().floor(e);
      }
    }

    @Override
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
      synchronized (mutex) {
        return Synchronized.navigableSet(delegate().headSet(toElement, inclusive), mutex);
      }
    }

    @Override
    public SortedSet<E> headSet(E toElement) {
      return headSet(toElement, false);
    }

        return delegate().floor(e);
      }
    }

    @Override
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
      synchronized (mutex) {
        return Synchronized.navigableSet(delegate().headSet(toElement, inclusive), mutex);
      }
    }

    @Override
    public SortedSet<E> headSet(E toElement) {
      return headSet(toElement, false);
    }

   * @since 12.0
   */
  @Override
  public ImmutableSortedMap<K, V> headMap(K toKey, boolean inclusive) {
    return getSubMap(0, keySet.headIndex(checkNotNull(toKey), inclusive));
  }

  /**
   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys ranges
   * from {@code fromKey}, inclusive, to {@code toKey}, exclusive.
   *