anchor.diff:    options = {
   
       networking.hosts = lib.mkOption {
  -      type = types.attrsOf ( types.listOf types.str );
  -      default = {};
  +      type = types.attrsOf (types.listOf types.str);
         example = literalExample ''
           {
             "127.0.0.1" = [ "foo.bar.baz" ];
  
positive.code:   resolvconfOptions = cfg.resolvconfOptions
      ++ optional cfg.dnsSingleRequest "single-request"
      ++ optional cfg.dnsExtensionMechanism "edns0";
  in
  
  {
  
negative.code:         "rpc".source = pkgs.glibc.out + "/etc/rpc";
  
          # /etc/hosts: Hostname-to-IP mappings.
          "hosts".text = let
            oneToString = set: ip: ip + " " + concatStringsSep " " set.${ip};
            allToString = set: concatMapStringsSep "\n" (oneToString set) (attrNames set);
          in ''
            ${allToString cfg.hosts}
            ${cfg.extraHosts}
          '';
  
          # /etc/host.conf: resolver configuration file
          "host.conf".text = cfg.hostConf;
  