Fixed bug: Cannot delete key if not present
rdflib does not reorder JOINs, so it is extremely sensible to the order of clauses in a query.
This reordering seems to be a big optimization.
Comment: rdflib *does* reorder triples inside a BGP, but I am not sure how you get multiple triples in a BGP.
For #28-gae-with-triple-store
Always use lazy joins...i.e. do not try to read e.g. all labels into a set, then process them individually
For #28-gae-with-triple-store