This module implements a simple cache. The cache takes a getter procedure with an input argument and an output and wraps it in such a way that querying the cache for this value will either fetch the value from the cache or call the getter and get the value while populating the cache. The cache also supports manually invalidating entries based on input argument, as well as the two strategies LeastRecentlyUsed and LeastRecentlyFetched which allows clearing either the entries that haven't been used for the longest, or which was fetched the longest time ago respectively. The implementation is fairly optimised, but further optimisations could be made.