avocado> v = g.addVertex(1);
Vertex(1)

avocado> e = g.addEdge(v, v, 2, "self", { weight: 10 })
Edge(2)

avocado> e.getPropertyKeys()
[ "weight" ]

avocado> e.setProperty("name", "Hugo");
Hugo

avocado> e.getPropertyKeys()
[ "weight", "name" ]