: Sets.union(inEdgeMap.keySet(), outEdgeMap.keySet());
        return Iterators.unmodifiableIterator(incidentEdges.iterator());
      }

      @Override
      public int size() {
        return IntMath.saturatedAdd(inEdgeMap.size(), outEdgeMap.size() - selfLoopCount);
      }

      @Override
      public boolean contains(@Nullable Object obj) {
        return inEdgeMap.containsKey(obj) || outEdgeMap.containsKey(obj);
      }