# rest of the code ...
    # the methods are naive methods and self explained.
    # `stack` variable could be considered as a global variable.
    def isBalanced(self, s: str, stack: deque) -> bool:
        c: str = s[0]
        
        if self.isOpenBracket(c):
            stack.append(c)
        else:
            stack_top: str = stack.pop()
            if not self.areBothBracketsBalanced(stack_top, c):
                print('\tnot-match: ', stack_top, c)

                return False
            
            if len(s) == 1 and len(stack) == 0:
                print('\tfinal-case OK')
                
                return True
        
        # New solution.
        new_sol: str = s[1:]
        
        if len(new_sol) > 0:
            return self.isBalanced(new_sol, stack)