Getting started with PyXPCOM, Part 3

import anydbm
from xpcom import components
class DbHashFactory:
    _com_interfaces_ = components.interfaces.DbHashFactory
    _reg_clsid_ = "{11f39cd7-b40c-42b6-9eaa-b1082d9fcdb1}"
    _reg_contractid_ = "Python.DbHashFactory"
    #_reg_registrar_ = Setup()  #Function that would be called at registration time
    _reg_desc_ = "Factory for persistent hash implementations"
    def open(self, fname):
        dbObj = anydbm.open(fname, "w")
        db = DbHash(fname, dbObj)
        return db
    def create(self, fname):
        dbObj = anydbm.open(fname, "n")
        db = DbHash(fname, dbObj)
        return db
RESERVED_PREFIX = "_pydbhash_"
class DbHash:
    _com_interfaces_ = components.interfaces.DbHash
    _reg_clsid_ = "{b4eec552-ebed-4039-94b8-1a2d5dd2db35}"
    _reg_contractid_ = "Python.DbHash"
    _reg_desc_ = "Persistent hash implementation"
    def __init__(self, fname, dbObj):
        #This is where we initialize any general state
        self._fname = fname
        self._db = dbObj
        pass
    def keys(self):
        keys = self._db.keys()
        rp = RESERVED_PREFIX
        rpl = len(RESERVED_PREFIX)
        filtered_keys = [ k for k in keys if k[:rpl] != rp]
        return filtered_keys
    def set(self, key, value):
        self._db[key] = value
        return
    def lookup(self, key):
        if self._db.has_key(key):
            return self._db[key]
        else:
            return None
    def has_key(self, key):
        return self._db.has_key(key)
    #Attributes
    def get_fname(self):
        return self._fname
    def get_comment(self):
        return self.lookup(RESERVED_PREFIX + "comment")
    def set_comment(self, comment):
        self.set(RESERVED_PREFIX + "comment", comment)
        retu