Construct a cache with least-recently-used policy.
lru_cache(size = 10000)The maximum number of results to keep.
A function f(key, value) which takes a string in the first parameter and a lazily evaluated value in the second. `f` will use the string key to retrieve a value from the cache, or return the matching item from the cache, or force the second argument and return that, remembering the result on future calls.
When the number of entries in the cache exceeds size, the least
recently accessed entries are removed.