input: Write a function in Python to sort a dictionary according to its values, in descending order. If the dictionary is empty, return an empty dictionary.
  assert sortDictionary({'apple': 2, 'banana': 3, 'mango': 1}) == {'banana': 3, 'apple': 2, 'mango': 1}
  assert sortDictionary({'a': 10, 'b': 5, 'c': 20}) == {'c': 20, 'a': 10, 'b': 5}
  assert sortDictionary({}) == {}
  assert sortDictionary({'x': 7}) == {'x': 7}
  assert sortDictionary({'book1': 1, 'book2': 3, 'book3': 2}) == {'book2': 3, 'book3': 2, 'book1': 1}
output: def sortDictionary(d):
      return {k: v for k, v in sorted(d.items(), key=lambda item: item[1], reverse=True)}