'Send a message (or messages)
If seq is specified, it is a sequence number.  This can help
eliminate problems with ordering.'

def _exec_send(self, session_id, msg, seq=None):

    ses = self._get_session(session_id)
    if (ses is None):
        return make_error('No    such    session')
    r = ses.rx(msg, seq)
    if (isinstance(r, dict) and ('result' in r)):
        r['result']['session'] = ses._session_id
    return r
