input: Write a function to identify if a string s has matching parentheses. If the string contains matching parentheses, return True, otherwise return False. A matching parentheses means that for every opening parenthesis '(', there is a corresponding closing parenthesis ')'. 
  def matching_paren(s):
      stack = []
      for char in s:
          if char == '(':
              stack.append(char)
          elif char == ')':
              if len(stack) == 0:
                  return False 
              stack.pop()
      
      if len(stack) == 0:
          return True
      else:
          return False
  
  assert matching_paren("()") == True
  assert matching_paren("(()") == False
  assert matching_paren("(())") == True
  assert matching_paren("()(())") == True
  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 len(stack) == 0:
                  return False 
              stack.pop()
      
      if len(stack) == 0:
          return True
      else:
          return False