message: add graph addVertex with no args
diff: @@ -45,6 +45,13 @@ void bind_graph(py::module &m) {
  g.addVertex(m);
  },
  "")
  + .def(
  + "addVertex",
  + [](xacc::Graph &g) {
  + HeterogeneousMap m;
  + g.addVertex(m);
  + },
  + "")
  .def(
  "setVertexProperties",
  [](xacc::Graph &g, const int index,
  