presto-main/src/main/java/io/prestosql/operator/HttpPageBufferClient.java/PageResponseHandler/getComplete
class PageResponseHandler:        private static boolean getComplete(Response response)
        {
            String bufferComplete = response.getHeader(PRESTO_BUFFER_COMPLETE);
            if (bufferComplete == null) {
                throw new PageTransportErrorException(format("Expected %s header", PRESTO_BUFFER_COMPLETE));
            }
            return Boolean.parseBoolean(bufferComplete);
        }