def METHOD_NAME(self, response_data: bytes) -> Any:
    # protocomm security2 FSM which interprets/forms
    # protobuf packets according to present state of session
    if (self.session_state == security_state.REQUEST1):
        self.session_state = security_state.RESPONSE1_REQUEST2
        return self.setup0_request()
    if (self.session_state == security_state.RESPONSE1_REQUEST2):
        self.session_state = security_state.RESPONSE2
        self.setup0_response(response_data)
        return self.setup1_request()
    if (self.session_state == security_state.RESPONSE2):
        self.session_state = security_state.FINISHED
        self.setup1_response(response_data)
        return None
    print('---- Unexpected state! ----')
    return None