} else {
              return Iterators.unmodifiableIterator(
                  Iterators.transform(
                      graph.adjacentNodes(node).iterator(),
                      (N adjacentNode) -> EndpointPair.unordered(node, adjacentNode)));
            }
          }
        };
    return nodeInvalidatableSet(incident, node);
  }

  @Override
  public int degree(N node) {