* <p>In an undirected network, this is equal to {@code edgeConnectingOrNull(nodeV, nodeU)}.
   *
   * @throws IllegalArgumentException if there are multiple parallel edges connecting {@code nodeU}
   *     to {@code nodeV}
   * @throws IllegalArgumentException if {@code nodeU} or {@code nodeV} is not an element of this
   *     network
   * @since 23.0
   */
  @Nullable E edgeConnectingOrNull(N nodeU, N nodeV);

  /**

    }

    @Override
    public @Nullable E edgeConnectingOrNull(N nodeU, N nodeV) {
      return delegate().edgeConnectingOrNull(nodeV, nodeU); // transpose
    }

    @Override
    public @Nullable E edgeConnectingOrNull(EndpointPair<N> endpoints) {
      return delegate().edgeConnectingOrNull(transpose(endpoints));
    }

    @Override

    }

    @Override
    public @Nullable E edgeConnectingOrNull(N nodeU, N nodeV) {
      return delegate().edgeConnectingOrNull(nodeV, nodeU); // transpose
    }

    @Override
    public @Nullable E edgeConnectingOrNull(EndpointPair<N> endpoints) {
      return delegate().edgeConnectingOrNull(transpose(endpoints));
    }

    @Override

        switch (edgesConnecting.size()) {
          case 0:
            assertThat(network.edgeConnectingOrNull(node, otherNode)).isNull();
            assertThat(network.hasEdgeConnecting(node, otherNode)).isFalse();
            break;
          case 1:
            assertThat(network.edgeConnectingOrNull(node, otherNode))
                .isEqualTo(edgesConnecting.iterator().next());