decode = async rawData => {
  const decoder = new Decoder(rawData)
  return {
    throttleTime: decoder.readInt32(),
    responses: decoder.readArray(decodeResponses),
    errorCode: decoder.readInt16(),
  }
}
OffsetFetch Response (Version: 3) => throttle_time_ms [responses] error_code
  throttle_time_ms => INT32
  responses => topic [partition_responses]
    topic => STRING
    partition_responses => partition offset metadata error_code
      partition => INT32
      offset => INT64
      metadata => NULLABLE_STRING
      error_code => INT16
  error_code => INT16