diff --git a/blockchain/proof_of_work.py b/blockchain/proof_of_work.py
index f0e8c3bfa..84e918656 100644
--- a/blockchain/proof_of_work.py
+++ b/blockchain/proof_of_work.py
@@ -1,25 +1,25 @@
 import hashlib
 import time
 
-
 def proof_of_work(difficulty: int) -> int:
     """
     Simulates a Proof of Work mining process.
 
-    The miner must find a nonce such that the hash of the nonce starts
-    with a specific number of leading zeros (difficulty)
+    The miner must find a nonce such that the hash of the nonce starts 
+    with a specific number of leading zeros (difficulty).
 
     Args:
-          difficulty (int): The number of leading zeros required in the hash.
+        difficulty (int): The number of leading zeros required in the hash.
+
     Returns:
-          int: The nonce value that solves the puzzle.
+        int: The nonce value that solves the puzzle.
 
     Example:
-          >>> result = proof_of_work(2)  # Difficulty of 2 should be fast
-          >>> isinstance(result, int)
-          True
+        >>> result = proof_of_work(2)  # Difficulty of 2 should be fast
+        >>> isinstance(result, int)
+        True
     """
-    prefix = "0" * difficulty
+    prefix = '0' * difficulty
     nonce = 0
     start = time.time()  # Timing starts