'Process the session_start event.
Typical actions for the session_start event are
requesting the roster and broadcasting an initial
presence stanza.
Arguments:
event -- An empty dictionary. The session_start
event does not provide any additional
data.'

def start(self, event):

    self.send_presence()
    self.get_roster()
    session = {'greeting': self.greeting, 'next': self._command_start, 'error': self._command_error}
    self['xep_0050'].start_command(jid=self.command_provider, node='greeting', session=session)
