How to mock an external service in Python with an anti-corruption facade

class AntiCorruptionFacade:
    """Mocks a real API while keeping the same interface."""
    
    def __init__(self, data_store):
        self._data_store = data_store
        self._calls = []
    
    def get_user(self, user_id):
        self._calls.append(f"get_user({user_id})")
        return self._data_store.get(user_id, {}).copy()
    
    def update_user(self, user_id, data):
        self._calls.append(f"update_user({user_id})")
        self._data_store[user_id] = data
        return True
    
    def get_calls(self):
        return self._calls.copy()

if __name__ == "__main__":
    # Simulate the external service's data
    external_store = {
        1: {"name": "Alice", "email": "alice@example.com"},
        2: {"name": "Bob", "email": "bob@example.com"}
    }
    
    # Client code uses the facade as if it's the real service
    facade = AntiCorruptionFacade(external_store)
    
    print("Initial user 1:", facade.get_user(1))
    print("Updating user 2:", facade.update_user(2, {"name": "Robert", "email": "robert@example.com"}))
    print("Updated user 2:", facade.get_user(2))
    print("Missing user 99:", facade.get_user(99))
    print("Call log:", facade.get_calls())