Function apply 

pub fn apply(root: &Html, ops: &[Op]) -> Html

Apply a patch to an Html value — the server-side model of what the browser does.

This exists so the differ can be tested against its own client: apply(old, diff(old, new)) == new is a property, checked below and re-checked by the end-to-end harness against the real browser. It is the Phase 0 stand-in for §4.8’s differential harness.