he default) then it uses the
queue's default, set with create_queue(),
which is usually UNBOUND.

If "unbound" is UNBOUND_ERROR then get() will raise an
ItemInterpreterDestroyed exception if the original interpreter
has been destroyed.  This does not otherwise affect the queue;
the next call to put() will work like normal, returning the next
item in the queue.

If "unbound" is UNBOUND_REMOVE then the item will be removed
from the queue as soon as the original interpreter is destroyed.
Be aware that this will introduce an imbalance between put()
and get() calls.

If "unbound" is UNBOUND then it is returned by get() in place
of the unbound item.
Nr