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.
  
  def sortDictionary(dictionary):
    if not dictionary:
      return {}
    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({'x': 3, 'y': 3, 'z': 3})=={'x': 3, 'y': 3, 'z': 3}
  assert sortDictionary({})=={}
  assert sortDictionary({'single': 42})=={'single': 42}
output: def sortDictionary(dictionary):
    if not dictionary:
      return {}
    sorted_list = sorted(dictionary.items(), key=lambda x: x[1], reverse=True)
    sorted_dictionary = dict(sorted_list)
    return sorted_dictionary