builtins.fetchTarball {url="https://github.com/NixOS/nixpkgs-channels/archive/b7bdf48e3fa6b90ea475a03ed159f397bd3c3c65.tar.gz"; sha256="0ap49yync5rwvr5qn0qb45x2yzzix2vhfqfljbampdhs0ncnhigi";}