updated docs

lib/src/store/rocksdb.rs

@@ -40,8 +40,9 @@ use std::str;
 /// assert_eq!(vec![quad], results.unwrap());
 ///
 /// // SPARQL query
-/// let prepared_query = connection.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default()).unwrap();
+/// let options = QueryOptions::default();
-/// let results = prepared_query.exec().unwrap();
+/// let prepared_query = connection.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", None).unwrap();
+/// let results = prepared_query.exec(&options).unwrap();
 /// if let QueryResult::Bindings(results) = results {
 ///     assert_eq!(results.into_values_iter().next().unwrap().unwrap()[0], Some(ex.into()));
 /// }