input: Write a function to check if a given string contains all the words from a provided list. If it contains all the words return True, otherwise return False. If both the input string and the list of words are empty, return True.
  def contains_words(input_string, words):
   if not input_string and not words:
   return True
   for word in words:
   if word.lower() not in input_string.lower():
   return False
   return True
  
  assert contains_words('This is a test', ['test', 'this', 'is']) == True
  assert contains_words('This is a test', ['test', 'this', 'not']) == False
  assert contains_words('Checking for words', []) == True
  assert contains_words('', ['test']) == False
  assert contains_words('', []) == True
output: def contains_words(input_string, words):
      if not input_string and not words:
          return True
      for word in words:
          if word.lower() not in input_string.lower():
              return False
      return True