[NTG-context] Saving module data in tuc file

Hi, How does one save and read third-party data in tuc file at the lua end? I am trying to write a module t-ifchanged that defines a \doiffilechanged macro that provides the functionality of mtxrun --ifchanged without calling an external program (This is meant to be a support module for t-vim, where the external calls to mtxrun are too time consuming). I can successfully write additional data to the tuc file, but cannot figure out how to initialize the data from tuc file. (See attached file). Any hints are welcome. Aditya