A lich is hit with True Resurrection. What happens?

So I am looking at undead immunities in Pathfinder e1 and I see this.

"Not affected by raise dead and reincarnate spells or abilities. Resurrection and true resurrection can affect undead creatures. These spells turn undead creatures back into the living creatures they were before becoming undead."

Would this cause the lich to return to life but retain all of its abilities, lose the template, or something else?

Edit: A lot of people are missing the point of this thread. I am not asking for can a person find a lich willing (people keep telling me no), I am asking for the what would happen if all conditions are met. No cop outs.