anchor.diff:  
     addrOpts = v:
       assert v == 4 || v == 6;
  -    {
  -      address = mkOption {
  -        type = types.str;
  -        description = ''
  -          IPv${toString v} address of the interface.  Leave empty to configure the
  -          interface using DHCP.
  -        '';
  -      };
  -
  -      prefixLength = mkOption {
  -        type = types.addCheck types.int (n: n >= 0 && n <= (if v == 4 then 32 else 128));
  -        description = ''
  -          Subnet mask of the interface, specified as the number of
  -          bits in the prefix (<literal>${if v == 4 then "24" else "64"}</literal>).
  -        '';
  +    { options = {
  +        address = mkOption {
  +          type = types.str;
  +          description = ''
  +            IPv${toString v} address of the interface.  Leave empty to configure the
  +            interface using DHCP.
  +          '';
  +        };
  +
  +        prefixLength = mkOption {
  +          type = types.addCheck types.int (n: n >= 0 && n <= (if v == 4 then 32 else 128));
  +          description = ''
  +            Subnet mask of the interface, specified as the number of
  +            bits in the prefix (<literal>${if v == 4 then "24" else "64"}</literal>).
  +          '';
  +        };
         };
       };
   
  
positive.code:         <option>networking.useDHCP</option> is true, then every
          interface not listed here will be configured using DHCP.
        '';
        type = types.loaOf types.optionSet;
        options = [ interfaceOpts ];
      };
  
      networking.vswitches = mkOption {
  
negative.code:       description = ''
          This option allows you to define 6-to-4 interfaces which should be automatically created.
        '';
        type = with types; attrsOf (submodule {
          options = {
  
            remote = mkOption {
              type = types.nullOr types.str;
              default = null;
              example = "10.0.0.1";
              description = ''
                The address of the remote endpoint to forward traffic over.
              '';
            };
  
            local = mkOption {
              type = types.nullOr types.str;
              default = null;
              example = "10.0.0.22";
              description = ''
                The address of the local endpoint which the remote
                side should send packets to.
              '';
            };
  
            ttl = mkOption {
              type = types.nullOr types.int;
              default = null;
              example = 255;
              description = ''
                The time-to-live of the connection to the remote tunnel endpoint.
              '';
            };
  
            dev = mkOption {
              type = types.nullOr types.str;
              default = null;
              example = "enp4s0f0";
              description = ''
                The underlying network device on which the tunnel resides.
              '';
            };
  
          };
  
        });
      };
  
      networking.vlans = mkOption {
  