input: Write a function to check if the string `s` contains matching parentheses. If the string has matching parentheses, return True; otherwise, return False. Use a stack data structure to solve this problem. If the input string is empty, 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