old_contents: #!/usr/bin/env python
  
  """
   Let's continue examining words. You are given two string with words separated by commas. Try to find what is common
   between these strings. The words are not repeated in the same string.
  
  Your function should find all of the words that appear in both strings. The result must be represented as a string of
  words separated by commas in alphabetic order.
  
  Input: Two arguments as strings.
  
  Output: The common words as a string.
  
  Precondition:
  Each string contains no more than 10 words.
  All words separated by commas.
  All words consist of lowercase latin letters.
  """
  
  
  def checkio(first, second):
      return ','.join(sorted(list(set(first.split(',')) & set(second.split(',')))))
  
  
  # These "asserts" using only for self-checking and not necessary for auto-testing
  if __name__ == '__main__':
      assert checkio("hello,world", "hello,earth") == "hello", "Hello"
      assert checkio("one,two,three", "four,five,six") == "", "Too different"
      assert checkio("one,two,three", "four,five,one,two,six,three") == "one,three,two", "1 2 3"
  
new_contents: #!/usr/bin/env python
  
  """
   Let's continue examining words. You are given two string with words separated by commas. Try to find what is common
   between these strings. The words are not repeated in the same string.
  
  Your function should find all of the words that appear in both strings. The result must be represented as a string of
  words separated by commas in alphabetic order.
  
  Input: Two arguments as strings.
  
  Output: The common words as a string.
  
  Precondition:
  Each string contains no more than 10 words.
  All words separated by commas.
  All words consist of lowercase latin letters.
  """
  
  
  def checkio(first, second):
      return ','.join(sorted(list(set(first.split(',')) & set(second.split(',')))))
  
  
  # These "asserts" using only for self-checking and not necessary for auto-testing
  def test_function():
      assert checkio("hello,world", "hello,earth") == "hello", "Hello"
      assert checkio("one,two,three", "four,five,six") == "", "Too different"
      assert checkio("one,two,three", "four,five,one,two,six,three") == "one,three,two", "1 2 3"
  
  if __name__ == '__main__':
      test_function()
subject: Add 2 checks