input: Write a function to take in two strings as input and return a list of all the words in both strings. Use the assert statement to test the function with the given examples. The function should return the list of words concatenated from both input strings.
  assert string_to_list("I want to make a difference", "The journey to success is long")==['I', 'want', 'to', 'make', 'a', 'difference', 'The', 'journey', 'to', 'success', 'is', 'long']
  assert string_to_list("hello world", "goodbye space")==['hello', 'world', 'goodbye', 'space']
  assert string_to_list("", "empty string")==['empty', 'string']
  assert string_to_list("no common words", "two separate phrases")==['no', 'common', 'words', 'two', 'separate', 'phrases']
  assert string_to_list("", "")==[]
output: def string_to_list(s1, s2):
      return s1.split() + s2.split()