[ZODB-Dev] [ZODB3-3.1] Why __delitem__ is not inherited from OOBTree?

[Ury Marshak]

In the following code:

-------------------------------------------------------
import ZODB
import Persistence
import BTrees.OOBTree

class WorkerList(BTrees.OOBTree.OOBTree):
    def __init__(self):
        BTrees.OOBTree.OOBTree.__init__(self)


wl = WorkerList()
wl[1] = 33
del wl[1]
-------------------------------------------------------

dies with:

Traceback (most recent call last):
  File "C:\WORk\Einav\tbtr.py", line 12, in ?
    del wl[1]
AttributeError: __delitem__

It works when I use IOBtree or IIBTree.
Dies on OOBTree and OIBTree. Is there some 
limitation when inheriting from object-keyed
BTrees?

Ury