Try to fix ruff

Author: MaximSmolskiy

Diff for: other/lfu_cache.py

@@ -24,8 +24,8 @@ def __init__(self, key: T | None, val: U | None):
         self.prev: DoubleLinkedListNode[T, U] | None = None
 
     def __repr__(self) -> str:
-        return f"Node: key: {self.key}, val: {self.val}, freq: {lf.freq}, "
-        "has next: {self.next is not None}, has prev: {self.prev is not None}"
+        return f"Node: key: {self.key}, val: {self.val}, freq: {self.freq}, "\
+               f"has next: {self.next is not None}, has prev: {self.prev is not None}"
 
 
 class DoubleLinkedList(Generic[T, U]):