Lua How to add a focus by NPC?

[MorganaSacani]

In this algorithm, I check if the NPC is focusing on myself:

if not npcHandler:isFocused(cid) then

    return false
end

My doubt is:
How to add a focus to my character? Which function to use?

@EDIT:
I searched within my server's NPC system and found the answer, so in case anyone has the same question. Here is the answer:

npcHandler:addFocus(cid)