anchor.diff:      nix = mkOption {
         default = pkgs: pkgs.nix;
         example = pkgs: pkgs.nixCustomFun /root/nix.tar.gz;
  -      description = ''
  +      description = "
           Use non-default Nix easily. Be careful, though, not to break everything.
  -      '';
  +      ";
       };
   
     };
  
positive.code:   nesting = {
      children = mkOption {
        default = [];
        description = ''
          Additional configurations to build.
        '';
      };
    };
  
  
negative.code:             ipAddress = "192.168.1.11";
            }
          ];
          description = "
            A list mapping ethernet addresses to IP addresses for the
            DHCP server.
          ";
        };
  
      };
  