Add as fn trait function

src/states.rs

@@ -11,6 +11,13 @@ pub trait FutureStateChange: Fn() -> Result<()> + Send + Sync {
     fn clone_box<'a>(&self) -> Box<dyn 'a + FutureStateChange>
     where
         Self: 'a;
+
+    fn as_fn(&self) -> &(dyn Fn() -> Result<()> + Send + Sync)
+    where
+        Self: Sized,
+    {
+        self
+    }
 }
 
 impl<F: Fn() -> Result<()> + Clone + Send + Sync> FutureStateChange for F {