Returns all messages and clears the stash. The stash is guaranteed to be empty afterwards.

TBD

Stashes the current message (the message that the actor received last)

Unstash the oldest message in the stash and prepends it to the actor's mailbox. The message is removed from the stash.

Unstashes all messages by prepending them to the actor's mailbox. The stash is guaranteed to be empty afterwards.

Unstashes all messages selected by the predicate function. Other messages are discarded. The stash is guaranteed to be empty afterwards.