input: Write a function to determine if a string s has matching parentheses. If the string contains matching parentheses, the function should return True, otherwise it should return False. If the string is empty, the function should return True.
  assert matching_paren("(())")==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