Added docstring for card_value

app.py

@@ -19,6 +19,17 @@ def blackjack_strategy(player_cards: list[str], dealer_card:str)-> str:
     Returns: Recommended action ("Hit", "Stand", or "Double Down"). 
     """
     def card_value(card: str) -> int:
+        """Converts a card string into its numeric value for Blackjack.
+        Args:
+            card: A string representing a playing card, where the first part is the rank 
+                  (2-10, J, Q, K, A) and the last character is the suit (H, D, C, S).
+
+        Returns:
+            int: The numeric value of the card:
+                 - A (Ace): 11
+                 - J, Q, K (Face cards): 10
+                 - Numeric cards: Their respective integer value
+        """
         if card[0] == 'A': return 11
         elif card[0] in 'KQJ': return 10
         else: return int(card[:-1])