input: Write a function to determine if a given string contains all the words from a specified list. The function should return True if all words are found in the string, and False otherwise.
  assert contains_words('This is a test', ['test', 'this', 'is'])==True
  assert contains_words('This is a test', ['test', 'hello'])==False
  assert contains_words('Python is awesome', ['python', 'is'])==True
  assert contains_words('Short String', ['very', 'long', 'words'])==False
  assert contains_words('', [''])==True
output: def contains_words(s, words):
      s_lower = s.lower()
      return all(word.lower() in s_lower for word in words)