[Zope] Standalone ZODB and OOBTree

[Luis N]

I'm having troubles opening and closing the standalone ZODB with an OOBTree.

def opendb():
    path = os.path.expanduser('~/zodb/zodb.fs')
    try:
        storage = FileStorage.FileStorage(path)
        db = DB(storage)
        conn = db.open()
        dbroot = conn.root()
        if not dbroot.has_key('authors'):
            dbroot['authors'] = OOBTree()
        dbroot = conn.root()
        return (dbroot, conn, db, storage)
    except:
        return False

def closedb(database):
    try:
        get_transaction.abort()
        database[0].close()
        database[1].close()
        database[2].close()
        return True
    except:
        return False

>>> db = opendb()
>>> db[0]
{'authors': <BTrees._OOBTree.OOBTree object at 0x82e1dac>}
>>> db[1]
<Connection at 082f6d6c>
>>> db[2]
<ZODB.DB.DB object at 0x81dd34c>
>>> closedb(db)
False
>>> db[0].close
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'PersistentMapping' object has no attribute 'close'
>>> db[1].close
<bound method Connection.close of <Connection at 082f6d6c>>
>>> db[2].close
<bound method DB.close of <ZODB.DB.DB object at 0x81dd34c>>

How should the OOBTree closed?