Module K1.BucketSource
A bucket is a mutable "list" of ephemerons.
Create a new bucket.
Add an ephemeron to the bucket.
remove b k removes from b the most-recently added ephemeron with key k, or does nothing if there is no such ephemeron.
Returns the data of the most-recently added ephemeron with the given key, or None if there is no such ephemeron.
Returns an upper bound on the length of the bucket.
Remove all ephemerons from the bucket.