{self, ...}: let
  forSelfOverlay =
    if builtins.hasAttr "overlays" self && builtins.hasAttr "forSelf" self.overlays
    then self.overlays.forSelf
    else (_: p: p);
in rec {
  systems = ["aarch64-linux" "aarch64-darwin" "x86_64-darwin" "x86_64-linux"];
  forSystems = nixpkgs: nixpkgs.lib.genAttrs systems;
  pkgsFor = nixpkgs: system: (import nixpkgs {inherit system;}).extend forSelfOverlay;
  genPkgs = nixpkgs: func: (forSystems nixpkgs (system: func (pkgsFor nixpkgs system)));
}