anchor.diff:        extraDomains = mkOption {
           type = types.attrsOf (types.nullOr types.str);
           default = {};
  -        example = {
  -          "example.org" = "/srv/http/nginx";
  -          "mydomain.org" = null;
  -        };
  +        example = literalExample ''
  +          {
  +            "example.org" = "/srv/http/nginx";
  +            "mydomain.org" = null;
  +          }
  +        '';
           description = ''
             Extra domain names for which certificates are to be issued, with their
             own server roots if needed.
  
positive.code:         description = ''
            Attribute set of certificates to get signed and renewed.
          '';
          example = {
            "example.com" = {
              webroot = "/var/www/challenges/";
              email = "foo@example.com";
              extraDomains = { "www.example.com" = null; "foo.example.com" = "/var/www/foo/"; };
            };
            "bar.example.com" = {
              webroot = "/var/www/challenges/";
              email = "bar@example.com";
            };
          };
        };
      };
    };
  
negative.code:         description = ''
            Where the webroot of the HTTP vhost is located.
            <filename>.well-known/acme-challenge/</filename> directory
            will be created below the webroot if it doesn't exist.
            <literal>http://example.org/.well-known/acme-challenge/</literal> must also
            be available (notice unencrypted HTTP).
          '';
  