Any better way of doing this: ```fun MutableMap&lt...

# codereview

[dave08]

Any better way of doing this:

fun MutableMap<String, Any>.mergeWith(mapOverride: Map<String, Any>?) {
	entries.forEach { baseMap ->
		val mainValue = baseMap.value
		if (mainValue is String) {
			val resolved = mapOverride?.get(baseMap.key) as? String
			resolved?.let { this.put(baseMap.key, resolved) }
		} else if (mainValue is Set<*>) {
			val resolved = mapOverride?.get(baseMap.key) as? Set<String>
			resolved?.let { 
				this.put(baseMap.key, (mainValue as Set<String>).union(resolved))
			}
		}
	}
}