'Handle the start of the session.
Arguments:
feature -- The stream features element.'

def _handle_start_session(self, features):

    iq = self.xmpp.Iq()
    iq['type'] = 'set'
    iq.enable('session')
    iq.send(now=True)
    self.xmpp.features.add('session')
    log.debug('Established    Session')
    self.xmpp.sessionstarted = True
    self.xmpp.session_started_event.set()
    self.xmpp.event('session_start')
