Topological sort using dfs

hii, please have a look at my code :


and tell me that what is wrong in the function topologicalsort_dfs and dfshelper.
in this i have used the original function that was taught in the dfs video and just added the line of adding an element in a linked list at the front.
the code that is taught in this video is only a little bit diiferent but my code is not working.