Pyfdt module not found

I need to use pyfdt module to build a package but I encountered following error:

warning: Git tree '/home/user/playground/riscv-communicator' is dirty
error: undefined variable 'pyfdt'

       at /nix/store/0pvk8dal0cbhmcm11zp6h2i53107f7g5-source/tii/tc-saluki/sel4/default.nix:17:54:

           16|   nativeBuildInputs = [ cmake ninja dtc
           17|    (python311.withPackages (ps: with ps; [ pip pyaml pyfdt ]))
             |                                                      ^
           18|   ];

pyfdt is valid python module, why is this error reported?