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))