return map(transformValues(delegate().rowMap(), m -> map(m, mutex)), mutex);
      }
    }

    @Override
    public Map<C, Map<R, V>> columnMap() {
      synchronized (mutex) {
        return map(transformValues(delegate().columnMap(), m -> map(m, mutex)), mutex);
      }
    }

    @Override
    public int hashCode() {
      synchronized (mutex) {

        return map(transformValues(delegate().rowMap(), m -> map(m, mutex)), mutex);
      }
    }

    @Override
    public Map<C, Map<R, V>> columnMap() {
      synchronized (mutex) {
        return map(transformValues(delegate().columnMap(), m -> map(m, mutex)), mutex);
      }
    }

    @Override
    public int hashCode() {
      synchronized (mutex) {