input: Write a function to check 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.
  def contains_words(input_string, words):
   for word in words:
   if word not in input_string:
   return False
   return True
  
  assert contains_words('This is a test', ['test', 'this', 'is'])==True
  assert contains_words('This is another test', ['another', 'test', 'is'])==True
  assert contains_words('Hello world', ['hello', 'world'])==False
  assert contains_words('A quick brown fox', ['quick', 'fox', 'dog'])==False
  assert contains_words('', ['test', 'this', 'is'])==False
output: def contains_words(input_string, words):
      for word in words:
          if word.lower() not in input_string.lower():
              return False
      return True