Added method to access union find without path compression from undo-log

Author: dewert99

src/raw/semi_persistent1.rs

@@ -220,4 +220,9 @@ impl<L: Language, U: AsUnwrap<UndoLog>> RawEGraph<L, (), U> {
     pub fn pop1(&mut self, info: PushInfo) {
         self.raw_pop1(info, |_, _, _| ())
     }
+
+    /// Return the direct parent from the union find without path compression
+    pub fn find_direct_parent(&self, id: Id) -> Id {
+        self.undo_log.as_unwrap().undo_find.parent(id)
+    }
 }