def delete(self):
        """Deletes the local marker file and also any data in the Fuseki
        server.

        """
        MetadataCache.delete(self)
        try:
            self.graph.query('DELETE WHERE { ?s ?p ?o . }')
        except ResultException:
            # this is often just a false positive since Jena Fuseki does not
            # return tuples for a deletion query, so swallowing the exception
            # here is fine
            logging.exception('error when deleting graph')
Deletes the local marker file and also any data in the Fuseki
        server.