def _has_four(self):
        '''
        Check the existence of four cards
        Returns:
            True: exist
            False: not exist
        '''
        if self.product == 5 or self.product == 10 or self.product == 15:
            return True
        else:
            return False

        Check the existence of four cards
        Returns:
            True: exist
            False: not exist
        
rlcard/games/limitholdem/utils.py