The New "import" keyword in H13

[abvariant]

Hello all!

I've noticed that in Houdini 13, within the directlighting VOP node, the outer code reads:
 

import directlighting;

Rather than the old way of specifying the whole function.

This is good.

But how do I import functions? Whenever I place "import directlighting;" in the outer code of any of my nodes, I get the following error:
Failed to import function 'directlighting'. (30,1:21)

In addition, I get an identical error when trying to import it within a header. Importing it in a header is what I actually want to do: my main aim is to call directlighting() from within a header.

What do I need to do to get imports working?

Thanks!