Script call "if actor learned skill"

Does someone know the script call for looking if a specific actor has learned/has not learned a specific skill?

if (ThisActor.isLearnedSkill(skillID))

Just replace ThisActor with whatever designation you need, like user or target, and replace skillID with the necessary number.

There is also a conditional branch for "has learned" so that you can use it in events without the need for scripting.

However @Klunky2 are you aware that there is a difference between "has learned" and "can use"?
Skills added by equipment will not show as "has learned", only the skills from the class level list and skills that are learned by event commands will be found that way.