let
  lib = (import <nixpkgs> { overlays = []; }).lib;
  composeOverlays = lib.foldl' lib.composeExtensions (self: super: {});
in
composeOverlays [(import ./overlay1.nix)
                 (import ./overlay2.nix)
                 (self: super: {package30 = self.htop; })
                ]