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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 WaitUntilNoFlowsToProcess(self, timeout=None):
 """Waits until flow processing thread is done processing flows. Args: timeout: If specified, is a max number of seconds to spend waiting. Raises: TimeOutWhileWaitingForFlowsToBeProcessedError: if timeout is reached. """

    t = self.flow_handler_thread
    if not t:
      return

    start_time = time.time()
    while True:
      with self.lock:
        # If the thread is dead, or there are no requests
        # to be processed/being processed, we stop waiting
        # and return from the function.
        if (not t.isAlive() or
            (not self._GetFlowRequestsReadyForProcessing() and
             not self.flow_handler_num_being_processed)):
          return

      time.sleep(0.2)

      if timeout and time.time() - start_time > timeout:
        raise TimeOutWhileWaitingForFlowsToBeProcessedError(
            "Flow processing didn't finish in time.")