docs: def getAllClasses(self, hide_base_schemas=True):
          """
          by default, obscure all RDF/RDFS/OWL/XML stuff
          2016-05-06: not obscured anymore
          """
          query = """SELECT DISTINCT ?x ?c
                   WHERE {
                           {
                               { ?x a owl:Class }
                               union
                               { ?x a rdfs:Class }
                               union
                               { ?x rdfs:subClassOf ?y }
                               union
                               { ?z rdfs:subClassOf ?x }
                               union
                               { ?y rdfs:domain ?x }
                               union
                               { ?y rdfs:range ?x }
                               # union
                               # { ?y rdf:type ?x }
                           } .
  
                           ?x a ?c
  
                      %s
  
                   }
                   ORDER BY  ?x
                   """
          if hide_base_schemas:
              query = query %  """FILTER(
                       !STRSTARTS(STR(?x), "http://www.w3.org/2002/07/owl")
                       && !STRSTARTS(STR(?x), "http://www.w3.org/1999/02/22-rdf-syntax-ns")
                       && !STRSTARTS(STR(?x), "http://www.w3.org/2000/01/rdf-schema")
                       && !STRSTARTS(STR(?x), "http://www.w3.org/2001/XMLSchema")
                       && !STRSTARTS(STR(?x), "http://www.w3.org/XML/1998/namespace")
                       && (!isBlank(?x))
                        ) ."""
          else:
              query = query % ""
  
          qres = self.rdfgraph.query(query)
          return list(qres)