input: Write a python function to sort a dictionary by its values in descending order.
  assert sort_dict_by_value({'apple': 3, 'banana': 1, 'cherry': 2}) == {'apple': 3, 'cherry': 2, 'banana': 1}
  assert sort_dict_by_value({'a': 10, 'b': 5, 'c': 20}) == {'c': 20, 'a': 10, 'b': 5}
  assert sort_dict_by_value({'x': 100, 'y': 50, 'z': 150}) == {'z': 150, 'x': 100, 'y': 50}
output: def sort_dict_by_value(d):
      return dict(sorted(d.items(), key=lambda item: item[1], reverse=True))