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