<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _start_reader_thread(self, stream, chunks):
 """Starts a thread for reading output from FFMPEG. The thread reads consecutive chunks from the stream and saves them in the given list. Args: stream: output stream of the FFMPEG process. chunks: list to save output chunks to. Returns: Thread """

    import io  # pylint: disable=g-import-not-at-top
    import threading  # pylint: disable=g-import-not-at-top
    def target():
      while True:
        chunk = stream.read(io.DEFAULT_BUFFER_SIZE)
        if not chunk:
          break
        chunks.append(chunk)
    thread = threading.Thread(target=target)
    thread.start()
    return thread