MAINT: Used f-string method

Updated the code with f-string methods wherever required for a better and cleaner understanding of the code.

Author: cyai

other/lru_cache.py

@@ -21,9 +21,7 @@ def __init__(self, key: T | None, val: U | None):
         self.prev: DoubleLinkedListNode[T, U] | None = None
 
     def __repr__(self) -> str:
-        return "Node: key: {}, val: {}, has next: {}, has prev: {}".format(
-            self.key, self.val, self.next is not None, self.prev is not None
-        )
+        return f"Node: key: {self.key}, val: {self.val}, has next: {self.next is not None}, has prev: {self.prev is not None}"
 
 
 class DoubleLinkedList(Generic[T, U]):