6.8.6.3 Executing UPDATE Queries Against a PGX Session
For now, there is no support for executing UPDATE queries
                        against a PgxSession and therefore, updates always have to
                        be executed against a PgxGraph. To obtain a graph from a session, use the
                                    PgxSession.getGraph(String graphName)
                        method.
               
Parent topic: Java APIs for Executing UPDATE Queries