From a branch I'm working on:

        if self.state == STATE_START and self.initiate_stanza is None:
            # we're the initiator: send session-initiate
            self.send_session_initiate()
        elif self.state == STATE_PENDING and self.initiate_stanza is not None:
            # the Telepathy end is the responder: send session-accept on its
            # behalf
            # FIXME: fd.o #26270: AddMembers, not SetRemoteCodecs, should be
            # the transition between PENDING and ACTIVE
            self.send_session_accept()
        else:
            # FIXME: fd.o #nnnnn: if only the parameters have changed, we can
            # send description-info
            logger.debug('already sent our codecs list, not sending it again')