Create a public class called Inverter with a single class method named invert. invert should accept a Map<String, Integer> and return a Map<Integer, String> with all of the key-value pairs swapped.

You can assert that the passed map is not null.

Because values are not necessarily unique in a map, normally you would need a way to determine what the right approach is when two keys map to the same value. However, the maps passed to your function will not have any duplicate values.