input: Write a function to determine if a given string contains all the words in a list of words. If the string contains all the words, return True, otherwise return False. The function should be case-insensitive and ignore spaces around the words.
  
  assert contains_words('This is a test', ['test', 'this', 'is'])==True
  assert contains_words('This is a test', ['test', 'this', 'a'])==True
  assert contains_words('This is a test', ['test', 'hello'])==False
  assert contains_words(' ', ['test'])==False
  assert contains_words('This is a test', [' '])==True
output: def contains_words(s, words):
      s = s.lower().strip()
      words = [word.lower().strip() for word in words]
      for word in words:
          if word and word not in s:
              return False
      return True