docs: def andify(list_of_strings):
      """
      Given a list of strings will join them with commas
      and a final "and" word.
  
      >>> andify(['Apples', 'Oranges', 'Mangos'])
      'Apples, Oranges and Mangos'
      """
      result = ', '.join(list_of_strings)
      comma_index = result.rfind(',')
      if comma_index > -1: result = result[:comma_index] + ' and' + result[comma_index+1:]
      return result