code: def and_join(strings):
      
      last = len(strings) - 1
      if last == 0:
          return strings[0]
      elif last < 0:
          return ''
      iterator = enumerate(strings)
      return ', '.join('and ' + s if i == last else s for i, s in iterator)
docs: Join the given ``strings`` by commas with last `' and '` conjuction.
  
      >>> and_join(['Korea', 'Japan', 'China', 'Taiwan'])
      'Korea, Japan, China, and Taiwan'
  
      :param strings: a list of words to join
      :type string: :class:`collections.abc.Sequence`
      :returns: a joined string
      :rtype: :class:`str`, :class:`basestring`