swap
Swaps dimensions in two-dimensional map. The returned map has keys from the second dimension as primary keys and primary keys are used in the second dimension.
inline fun <K1, K2, K3, KR1, KR2, KR3, V> Map<K1, Map<K2, Map<K3, V>>>.swapKeys(transform: (K1, K2, K3) -> Triple<KR1, KR2, KR3>): Map<KR1, Map<KR2, Map<KR3, V>>>(source)
Works similarly as swapKeys but the final map has three levels. transform specifies how the keys should be swapped (or modified) in the newly created map.