input: Write a python function to sort a dictionary by its values in descending order.
  assert sort_dict_by_value({'a': 3, 'b': 1, 'c': 5, 'd': 4, 'e': 2}) == [('c', 5), ('d', 4), ('a', 3), ('e', 2), ('b', 1)]
  assert sort_dict_by_value({'x': 10, 'y': 7, 'z': 15, 'w': 8}) == [('z', 15), ('x', 10), ('w', 8), ('y', 7)]
  assert sort_dict_by_value({'m': 2, 'n': 3, 'o': 1}) == [('n', 3), ('m', 2), ('o', 1)]
output: def sort_dict_by_value(d):
      return sorted(d.items(), key=lambda item: item[1], reverse=True)