diff --git a/blockchain/proof_of_work.py b/blockchain/proof_of_work.py
index 4bf14106b..f0e8c3bfa 100644
--- a/blockchain/proof_of_work.py
+++ b/blockchain/proof_of_work.py
@@ -1,31 +1,32 @@
 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)
-  
-  Args:
-        difficulty (int): The number of leading zeros required in the hash.
-  Returns:
-        int: The nonce value that solves the puzzle.
-        
-  Example:
-        >>> result = proof_of_work(2)  # Difficulty of 2 should be fast
-        >>> isinstance(result, int)
-        True
-    """
-  prefix = '0' * difficulty
-  nonce = 0
-  start = time.time()  # Timing starts
 
-  while True:
-      hash_result = hashlib.sha256(f"{nonce}".encode()).hexdigest()
-      if hash_result.startswith(prefix):
-          end = time.time()  # Timing ends
-          print(f"Time taken: {end - start:.2f}s")  # Print time taken
-          return nonce
-      nonce += 1
+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)
+
+    Args:
+          difficulty (int): The number of leading zeros required in the hash.
+    Returns:
+          int: The nonce value that solves the puzzle.
+
+    Example:
+          >>> result = proof_of_work(2)  # Difficulty of 2 should be fast
+          >>> isinstance(result, int)
+          True
+    """
+    prefix = "0" * difficulty
+    nonce = 0
+    start = time.time()  # Timing starts
+
+    while True:
+        hash_result = hashlib.sha256(f"{nonce}".encode()).hexdigest()
+        if hash_result.startswith(prefix):
+            end = time.time()  # Timing ends
+            print(f"Time taken: {end - start:.2f}s")  # Print time taken
+            return nonce
+        nonce += 1