Is replacing a rule in renderer.rules a public API?

[shepmaster]

I want to add some basic safety checks to what HTML tags and attributes are allowed. Some playing around has shown that I can do something like this:

const original = instance.renderer.rules.htmltag;
instance.renderer.rules.htmltag = function myHtmltag(tokens, idx /*, options, env */) {
  const content = tokens[idx].content;
  
  if (someMagicTest(content)) {
    return original(tokens, idx);
  } else {
    return escapeHtml(content);
  }
};

However, it's not abundantly clear to me if this is an approved method, and I don't want to build on a private API that is subject to change.