the third argument in .data() method

the third argument in .data() method

hi there, I found something odd ( I think ) , in the owl carousel plugin . previously, I was a junior in js.

I have read .data() on api.jquery . and I see this method only can enter a maximum two arguments . while at the plugin I see the developers enter the third variable .

for what the third variable is?
while at the api.jquery only 2 arguments .

the code is:
$.data(this, "owlCarousel", carousel);
on line 1448.

thanks before. and sorry for my english.