Function seed_key 

pub fn seed_key() -> &'static str

The key the per-instance maps are SEEDED with, purely to give themselves a type.

★ IT MUST NOT BE A KEY ANY INSTANCE COULD HAVE, and the root key "" is. Seeded with "", the timer maps reported the ROOT instance as already known on its first render — so its countdown was never armed and the page’s clock never started, silently. An instance key is a path built from component names, so a leading control character can never collide with one.