minor adjustments

src/performance.rs

@@ -223,8 +223,7 @@ impl PyPerformance {
 
         perf = self.apply(perf);
         let state = perf.generate_state();
-        let x = perf.calculate();
-        let mut attrs = PyPerformanceAttributes::from(x);
+        let mut attrs = PyPerformanceAttributes::from(perf.calculate());
         attrs.state = Some(state.into());
 
         Ok(attrs)

src/strains.rs

@@ -8,7 +8,7 @@ use crate::mode::PyGameMode;
 type DoubleList = Vec<f64>;
 
 define_class! {
-    #[pyclass(name = "Strains")]
+    #[pyclass(name = "Strains", frozen)]
     #[derive(Default)]
     pub struct PyStrains {
         pub mode: PyGameMode!,