A disnix manual example appears to be missing crucial parts

[unappetizing-morsel]

"Example 4.6. Simplified intra-dependency composition for the StaffTracker" from section "4.3.3. Intra-dependency composition" appears to be missing some code and is not a well-formed nix expression on its own.

The example in question with foot notes removed:

{system, pkgs}:

let
  callPackage = pkgs.lib.callPackageWith (pkgs // self);
  
  self = {
  ### Databases
    rooms = callPackage ../pkgs/databases/rooms { };
  
    staff = callPackage ../pkgs/databases/staff { };
  
    zipcodes = callPackage ../pkgs/databases/zipcodes { };

  ### Web services + Clients
    ZipcodeService = callPackage ../pkgs/webservices/ZipcodeService { };
  
    ZipcodeServiceClient = callPackage ../pkgs/webservices/ZipcodeServiceClient { };
    
    ...
  
  ### Web applications
    StaffTracker = callPackage ../pkgs/webapplications/StaffTracker { };
  };
}

The let expression is opened but not paired with an in and does not have a nix expression to modify the context of. The trailing closing curly brace has no matching opening pair.

Something got lost in translation somewhere or wasn't finished up as intended?