How to use nix channels with nixops?

for example in my local machine I use nixpkgs = import <nixpkgs> {}; to use nixpkgs channel. How do I use the same technique for nixops deployment file?

As I do not have a deployment target right now I can’t test, but shouldn’t it work exactly like that as well?

I think this is how nixops works, through <nixpkgs>. E.g., if I am on unstable and want to use 19.09, I run the following:

export NIX_PATH=nixpkgs=

before running nixops.