fix: code cleanup, documentation

src/optimization/mod.rs

@@ -5,8 +5,7 @@ pub type F<'a, T, X> = dyn for<'b> Fn(&'b X) -> T + 'a;
 pub type DF<'a, X> = dyn for<'b> Fn(&'b mut X, &'b X) + 'a;
 
 #[derive(Debug, PartialEq)]
-pub enum FunctionOrder {
-    FIRST,
+pub enum FunctionOrder {    
     SECOND,
     THIRD,
 }