input: Write a function that takes in a string and a list of words and returns true if the string contains all the words in the list. Use case-insensitive comparison.
  
  def contains_words(input_string, words):
   for word in words:
   if word.lower() not in input_string.lower():
   return False
   return True
  
  print(contains_words('This is a test', ['test', 'this', 'is'])) # True
  print(contains_words('This is a test', ['Test', 'This', 'Is'])) # True
  print(contains_words('This is a test', ['fails', 'this'])) # False
output: def contains_words(input_string, words):
   for word in words:
   if word.lower() not in input_string.lower():
   return False
   return True