*
   * <p>If this network {@link #allowsParallelEdges() allows parallel edges}, parallel edges will be
   * treated as if collapsed into a single edge. For example, the {@link #degree(Object)} of a node
   * in the {@link Graph} view may be less than the degree of the same node in this {@link Network}.
   */
  Graph<N> asGraph();

  //
  // Network properties
  //

  /**

    putEdge(N1, N1);
    assertThat(graph.degree(N1)).isEqualTo(2);
    putEdge(N1, N2);
    assertThat(graph.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.inDegree(N1)).isEqualTo(2);
    putEdge(N1, N2);
    assertThat(graph.inDegree(N1)).isEqualTo(3);
  }

  @Test

    putEdge(N1, N1);
    assertThat(graph.degree(N1)).isEqualTo(2);
    putEdge(N1, N2);
    assertThat(graph.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.inDegree(N1)).isEqualTo(1);
    putEdge(N4, N1);
    assertThat(graph.inDegree(N1)).isEqualTo(2);
  }

  @Test

        assertThat(network.outEdges(node)).isEqualTo(network.incidentEdges(node));
        assertThat(network.inDegree(node)).isEqualTo(network.degree(node));
        assertThat(network.outDegree(node)).isEqualTo(network.degree(node));
      }

      for (N otherNode : network.nodes()) {
        Set<E> edgesConnecting = sanityCheckSet(network.edgesConnecting(node, otherNode));

    putEdge(N1, N1);
    assertThat(graph.degree(N1)).isEqualTo(2);
    putEdge(N1, N2);
    assertThat(graph.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.inDegree(N1)).isEqualTo(2);
    putEdge(N1, N2);
    assertThat(graph.inDegree(N1)).isEqualTo(3);
  }

  @Test

    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(1);
    addEdge(N4, N1, E41);
    assertThat(network.inDegree(N1)).isEqualTo(2);
  }

  @Test

    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(1);
    addEdge(N4, N1, E41);
    assertThat(network.inDegree(N1)).isEqualTo(2);
  }

  @Test

    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.inDegree(N1)).isEqualTo(3);
  }

  @Test

    AbstractGraphTest.validateGraph(transpose);

    for (Integer node : directedGraph.nodes()) {
      assertThat(directedGraph.inDegree(node)).isSameInstanceAs(transpose.outDegree(node));
      assertThat(directedGraph.outDegree(node)).isSameInstanceAs(transpose.inDegree(node));
    }

    assertThat(transpose.successors(N1)).doesNotContain(N2);
    directedGraph.putEdge(N2, N1);
    // View should be updated.

        }
      };
    }

    @Override
    public int inDegree(N node) {
      return delegate().outDegree(node); // transpose
    }

    @Override
    public int outDegree(N node) {
      return delegate().inDegree(node); // transpose
    }

    @Override
    public boolean hasEdgeConnecting(N nodeU, N nodeV) {