input: Write a function to determine if a given string contains all the words from a provided list of words. The function should return True if all words are found in the string, otherwise it should 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 a test', ['test', 'a', 'not'])==False
  assert contains_words('Python is fun', ['Python', 'fun'])==True
  assert contains_words('Hello world', ['Hello', 'world'])==True
  assert contains_words('', ['a', 'b'])==False
output: def contains_words(input_string, words):
      for word in words:
          if word.lower() not in input_string.lower():
              return False
      return True