code: public Set<DirectedTypedEdge<T>> edges(T t) {
          Set<DirectedTypedEdge<T>> edges =
              new HashSet<DirectedTypedEdge<T>>();
          for (SparseDirectedTypedEdgeSet<T> set :
                   vertexToEdges.valueCollection()) {
              Set<DirectedTypedEdge<T>> edgesOfType = set.getEdges(t);
              if (!edgesOfType.isEmpty())
                  edges.addAll(edgesOfType);
          }
          return edges;
      }
docs: {@inheritDoc}