inline fun <K : Any, V> nullableValueMap(map: Map<K, V>): Map<K, V?>Turns a Map into a map with a nullable value type.
Intended to be used in conjunction with platform types
such as Map<Int!, String!`>! or in other words, when you deal with Java and you want to turn a platform type into a
nullable type.
Basically it is a replacement for cast but without introducing one explicitly (we only give an additional hint to the
compiler that we expect a nullable type and not a non-nullable one). For instance, instead of writing
getPersons() as Map<String, Person?> you can write nullableValueMap(getPersons())