docs: def _load(self, graph, source):
          """from https://rdflib.readthedocs.io/en/stable/_modules/rdflib/plugins/sparql/sparql.html"""
          try:
              return graph.load(source)
          except:
              pass
          try:
              return graph.load(source, format='n3')
          except:
              pass
          try:
              return graph.load(source, format='nt')
          except:
              raise Exception("Could not load {} as either RDF/XML, N3 or NTriples".format(source))