Hi Nick,
I believe inline_0 is a temp function. If you will look at the code in it its not possible to run it on psql. Situation such as you need to select a value into a var and use this var on another operation or have a if and then clause. So inorder for you to perform things that can only be done in a function you create a temp function. I have done this for some of my create and even drop scripts although I did not use inline_0. Maybe its a name convention. Not sure though.
Maybe someone with more experience can further elaborate on this or contradict my explanation.