Is there a standalone Nixpkgs “standard library” to create private Nixpkgs repos?

Is there any project/repo that contains "standard library" functions extracted from the Nixpkgs repo?

Currently reading the Nixpkgs manual, and it seems that the Nixpkgs repo consists of

• functions that actually help build (cross-platform) packages (written using the Nix builtin's/primitives)
• collection of packages

Tried to find decentralization examples, but there aren't many (or I didn't find them). I like Cachix and the philosophy behind it, but that is for already built packages (unless I misunderstand something, which is more than possible).

Some of the resources found:

• Managing private Nix packages outside the Nixpkgs tree [Sander van der Burg]
• I create a local repository for NixOS/nixpkgs? [Unix/Linux Stack Exchange]

EDIT: Just found out about Nix User Repository (NUR).

EDIT2: Here's the thread on NixOS discourse.

Nixpkgs is a "megarepo", bundling highly related Nix projects, such as Nixpkgs, its standard library, NixOS and such. I am not aware of any other source or 'mirror' of these projects. If you want this to change, you can help out with the Nix Flakes idea/project/projects.

Today, if you only really need pkgs.lib, you can use lib = import <nixpkgs/lib>.