Python program involving topological sort

what's a coded program of a topological sort in python involving strings that takes tasks and outputs either a valid order or a word cycle if the list contains a cycle of any size

the tasks are put in a .list file and the program will input and output via standard input and output, an example of a .list is

learn python Read the python tutorial do exercise 1 learn python

and the solution for the list is

Read the python tutorial learn python do exercise 1

an example of a cycle list

get a job have experience have experience work on a job work on a job get a job

the answer for this list is

cycle