private boolean isEmpty() {
            return lines.isEmpty();
        }
Translates a contiguous range of bytes into a set of highlight blocks defined in terms
of line/col positions in the rendered hex dump. It highlights both the middle hex pairs
block and the right hand decoded chars column. For example a range of bytes that spans
two lines of the hex dump will result in four highlight {@link TextRange}s, two for the
two hex pair lines and two for the two decoded chars lines.
stroom-util/src/main/java/stroom/util/string/HexDumpUtil.java