arangodb/Documentation/Examples/graph-vertex-get-property-keys

arango> v = g.addVertex(1, { name : "Hugo" });
Vertex(1)

arango> v.getPropertyKeys();
[ "name" ]

arango> v.setProperty("email", "hugo@hugo.de");
"hugo@hugo.de"

arango> v.getPropertyKeys();
[ "name", "email" ]