Given input raw string (even with backslash escaped double quotes), output new string with every character in the string prepended with the ̲ HTML escape code "combining low line", which more or less ends up looking like underlined text.
r""""You need a 2\"x3\" """
̲"̲Y̲o̲u̲ ̲n̲e̲e̲d̲ ̲a̲ ̲2̲\\̲"̲x̲3̲\\̲"
When put into a Markdown document (like this README), it renders thusly:
̲"̲Y̲o̲u̲ ̲n̲e̲e̲d̲ ̲a̲ ̲2̲\̲"̲x̲3̲\̲"