fix issue with same names causing 0 index debruijn for var

crates/uplc/src/debruijn/bimap.rs

@@ -4,6 +4,8 @@ use crate::ast::Unique;
 
 use super::Level;
 
+#[derive(Debug)]
+
 pub struct BiMap {
     left: HashMap<Unique, Level>,
     right: HashMap<Level, Unique>,
@@ -22,6 +24,11 @@ impl BiMap {
         self.right.insert(level, unique);
     }
 
+    pub(super) fn remove(&mut self, unique: Unique, level: Level) {
+        self.left.remove(&unique);
+        self.right.remove(&level);
+    }
+
     pub(super) fn get(&self, unique: &Unique) -> Option<&Level> {
         self.left.get(unique)
     }