nix attrset stringifier

thang.nix

{
  __toString =
    self:
    let
      keys = builtins.filter (n: n != "__toString") (builtins.attrNames self);
      pairs = builtins.map (key: "  ${key} = ${self.${key}};") keys;
    in
    builtins.concatStringsSep "\n" (
      builtins.concatLists [
        [ "{" ]
        pairs
        [ "}" ]
      ]
    );
}