input: Write a function that sorts a dictionary by its values in descending order and returns 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
  
  
  ### Example Test Cases:
  
  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': 2, 'y': 2, 'z': 1}) == {'x': 2, 'y': 2, 'z': 1}
  
output: def sortDictionary(dictionary):
      sorted_list = sorted(dictionary.items(), key=lambda x: x[1], reverse=True)
      sorted_dictionary = dict(sorted_list)
      return sorted_dictionary