Implement Garbage Collection

storage_engine/src/index.rs

@@ -100,6 +100,11 @@ where
         Ok(())
     }
 
+    pub async fn reset(&mut self, data: BTreeMap<K, HashSet<V>>) -> Result<()> {
+        self.data = data;
+        self.sync_to_disk().await
+    }
+
     async fn append_to_file(&mut self, key: &K, value: &V) -> Result<()> {
         let mut encoded = Vec::new();
         encoded.extend(encode(key)?);