Identify the bug in the following code snippet implementing the strategy pattern for payment processing:

Identify the bug in the following code snippet implementing the strategy pattern for payment processing:

class PaymentProcessor:
    def __init__(self, strategy: PaymentStrategy):
        self.strategy = strategy

    def pay(self, amount):
        if isinstance(self.strategy, CreditCardStrategy):
            print(f"Processing credit card payment of ${amount}")
        elif isinstance(self.strategy, UPIStrategy):
            print(f"Processing UPI payment of ${amount}")
        else:
            print("Invalid payment method")