docs: def _feed_stream(feeder, in_stream, out_stream, block_size = BLOCK_SIZE):
      'Uses feeder to read and convert from in_stream and write to out_stream.'
  
      while True:
          chunk = in_stream.read(block_size)
          if not chunk:
              break
          converted = feeder.feed(chunk)
          out_stream.write(converted)
      converted = feeder.feed()
      out_stream.write(converted)