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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _recv_sf(self, data):
 """Process a received 'Single Frame' frame"""

        self.rx_timer.cancel()
        if self.rx_state != ISOTP_IDLE:
            warning("RX state was reset because single frame was received")
            self.rx_state = ISOTP_IDLE

        length = six.indexbytes(data, 0) & 0xf
        if len(data) - 1 < length:
            return 1

        msg = data[1:1 + length]
        self.rx_queue.put(msg)
        for cb in self.rx_callbacks:
            cb(msg)
        self.call_release()
        return 0