Find map keys that start with a given String

MapExtension.kt

fun <V> Map<String,V>.startsWith(search:String):V? {
    val reducedMap = this.toSortedMap().tailMap(search)
    if (!reducedMap.isEmpty() && reducedMap.firstKey().startsWith(search)) {
        return reducedMap.values.first()
    }

    return null
}