input: def sortDictionary(dictionary):
      """
      Sort a dictionary according to its values in descending order.
      >>> sortDictionary({'apple': 2, 'banana': 3, 'mango': 1})
      {'banana': 3, 'apple': 2, 'mango': 1}
      """
output:     sorted_items = sorted(dictionary.items(), key=lambda item: item[1], reverse=True)
      return dict(sorted_items)