input: Write a function that takes a string and a list of words as inputs and returns True if the string contains all the words in the list, otherwise returns 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 a test', ['test', 'hello']) == False
  assert contains_words('Hello world', []) == True
  assert contains_words('', ['test']) == False
  assert contains_words('The quick brown fox', ['quick', 'fox', 'brown']) == True
output: def contains_words(input_string, words):
      for word in words:
          if word.lower() not in input_string.lower():
              return False
      return True