Map package:stm-containers
Hash-table, based on STM-specialized Hash Array Mapped Trie.
Bidirectional map. Essentially, a bijection between subsets of its two
argument types.
For one value of the left-hand type this map contains one value of the
right-hand type and vice versa.
A multimap, based on an STM-specialized hash array mapped trie.
Basically it's just a wrapper API around
Map key
(Set value).