'Create a roster node for a JID.
Arguments:
xmpp -- The main SleekXMPP instance.
jid  -- The JID that owns the roster.
db   -- Optional interface to an external datastore.'

def __init__(self, xmpp, jid, db=None):

    self.xmpp = xmpp
    self.jid = jid
    self.db = db
    self.auto_authorize = True
    self.auto_subscribe = True
    self.last_status = None
    self._version = ''
    self._jids = {}
    self._last_status_lock = threading.Lock()
    if self.db:
        if hasattr(self.db, 'version'):
            self._version = self.db.version(self.jid)
        for jid in self.db.entries(self.jid):
            self.add(jid)
