input: Write a function to determine if a string contains matching parentheses. If it does, return True, otherwise return False.
  assert matching_paren("()") == True
  assert matching_paren("()()") == True
  assert matching_paren("(") == False
  assert matching_paren("((") == False
  assert matching_paren(")(") == False
output: def matching_paren(s):
      count = 0
      for char in s:
          if char == '(':
              count += 1
          elif char == ')':
              count -= 1
          if count < 0:
              return False
      return count == 0