public V put(@ParametricNullness K key, @ParametricNullness V value) {
    return putInBothMaps(key, value, false);
  }

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V forcePut(@ParametricNullness K key, @ParametricNullness V value) {
    return putInBothMaps(key, value, true);
  }

  @CheckForNull
  private V putInBothMaps(@ParametricNullness K key, @ParametricNullness V value, boolean force) {