Revert id change, and added method to get keys instead.

src/storage.rs

@@ -42,11 +42,15 @@ impl Storage {
         &mut self.items[id]
     }
 
-    pub fn items(&mut self) -> impl Iterator<Item = (usize, &Item)> {
+    pub fn items(&mut self) -> impl Iterator<Item = &Item> {
-        self.items.iter().enumerate()
+        self.items.iter()
     }
 
     pub fn items_mut(&mut self) -> impl Iterator<Item = &mut Item> {
         self.items.iter_mut()
     }
+
+    pub fn keys(&mut self) -> impl Iterator<Item = &String> {
+        self.keys.keys()
+    }
 }