input: Write a function to determine if a string `s` has matching parentheses. If the string contains matching parentheses, return True, otherwise return False. If the input string is empty, return True.
  assert matching_paren("((()))")==True
  assert matching_paren("()()()")==True
  assert matching_paren("(()))")==False
  assert matching_paren("(()(")==False
  assert matching_paren("")==True
output: def matching_paren(s):
      stack = []
      for char in s:
          if char == '(':
              stack.append(char)
          elif char == ')':
              if not stack:
                  return False
              stack.pop()
      return len(stack) == 0