<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def recv(self, timeout=None):
 """Receive an ISOTP frame, blocking if none is available in the buffer for at most 'timeout' seconds."""


        try:
            return self.rx_queue.get(timeout is None or timeout > 0, timeout)
        except queue.Empty:
            return None