input: Write a function to sort a dictionary according to its values in descending order. The function should take a dictionary as input and return the sorted dictionary.
  
  def sortDictionary(dictionary):
      sorted_list = sorted(dictionary.items(), key=lambda x: x[1], reverse=True)
      sorted_dictionary = dict(sorted_list)
      return sorted_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({'one': 1, 'two': 2, 'three': 3}) == {'three': 3, 'two': 2, 'one': 1}
  assert sortDictionary({}) == {}
output: def sortDictionary(dictionary):
      sorted_list = sorted(dictionary.items(), key=lambda x: x[1], reverse=True)
      sorted_dictionary = dict(sorted_list)
      return sorted_dictionary