/* Modify and return the given map as follows: for this problem the map may or may not contain the "a" and "b" keys. If both keys are present, append their 2 string values together and store the result under the key "ab". mapAB({"a": "Hi", "b": "There"}) → {"a": "Hi", "ab": "HiThere", "b": "There"} mapAB({"a": "Hi"}) → {"a": "Hi"} mapAB({"b": "There"}) → {"b": "There"} */ public class MapAB { }