return headMap(key, false).lastEntry();
  }

  @Override
  public @Nullable K lowerKey(@ParametricNullness K key) {
    return delegate().lowerKey(key);
  }

  /**
   * A sensible definition of {@link #lowerKey} in terms of {@code lowerEntry}. If you override
   * {@link #lowerEntry}, you may wish to override {@code lowerKey} to forward to this
   * implementation.
   */

    return headMap(key, false).lastEntry();
  }

  @Override
  public @Nullable K lowerKey(@ParametricNullness K key) {
    return delegate().lowerKey(key);
  }

  /**
   * A sensible definition of {@link #lowerKey} in terms of {@code lowerEntry}. If you override
   * {@link #lowerEntry}, you may wish to override {@code lowerKey} to forward to this
   * implementation.
   */

      Entry<K, Collection<V>> entry = sortedMap().lowerEntry(key);
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override
    public @Nullable K lowerKey(@ParametricNullness K key) {
      return sortedMap().lowerKey(key);
    }

    @Override
    public @Nullable Entry<K, Collection<V>> floorEntry(@ParametricNullness K key) {
      Entry<K, Collection<V>> entry = sortedMap().floorEntry(key);