{ inputs = { nixstable.url = "nixpkgs/21.05"; nixpkgs.url = "nixpkgs/nixos-unstable"; flake-utils.url = "github:numtide/flake-utils"; }; outputs = { self, nixpkgs, nixstable, flake-utils }: flake-utils.lib.eachDefaultSystem (system: let pkgs = nixpkgs.legacyPackages.${system}; stable = nixstable.legacyPackages.${system}; in { devShell = pkgs.mkShell { buildInputs = [ pkgs.epubcheck pkgs.nixfmt pkgs.nodejs-16_x pkgs.pandoc pkgs.pdftk pkgs.python39Full pkgs.python39Packages.weasyprint pkgs.jq pkgs.s3cmd ]; }; }); }