unable to access `namespace` in overlays

I am facing this error when trying to access namespace in my overlays/default/default.nix file.

Am I doing something wrong w.r.t the overlay docs?

error:
       … while evaluating a branch condition
         at /nix/store/45p0ynsaqkavq8b0hz6qnn5jysxa4whs-source/flake.nix:54:13:
           53|             name: value:
           54|             if isAttrs value then
             |             ^
           55|               lhs.${name} or { } // value

       … while calling the 'isAttrs' builtin
         at /nix/store/45p0ynsaqkavq8b0hz6qnn5jysxa4whs-source/flake.nix:54:16:
           53|             name: value:
           54|             if isAttrs value then
             |                ^
           55|               lhs.${name} or { } // value

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: function 'anonymous lambda' called without required argument 'namespace'
       at /nix/store/c4cl90bvylskmpcxqvv06jwd8z19g63k-7zj60sd46hsmjmv2s7fp3hkbz78fivz7-source/overlays/default/default.nix:1:1:
            1| { lib, namespace, ... }:
             | ^
            2| final: prev: {

Read the linked overlay documentation and inspect overlays/default/default.nix, then reproduce the error with the full stack trace. Done means determining why namespace is unavailable in that overlay context and clarifying or correcting the documented usage.