input: Write a python function to invert a dictionary, i.e., swap keys and values.
  assert invert_dictionary({"x": 7, "y": 8}) == {7: "x", 8: "y"}
  assert invert_dictionary({"a": 1, "b": 2, "c": 3}) == {1: "a", 2: "b", 3: "c"}
  assert invert_dictionary({1: "one", 2: "two"}) == {"one": 1, "two": 2}
output: def invert_dictionary(d):
      return {v: k for k, v in d.items()}