methods which was called by test.py know called by topological_sort.py

functionality of test.py was inserted to topological_sort.py to simplify
program for user and more code understability
main change is  new method sort

there was  several changes first there new variable is_graph_dag  of
bool type, which says graph dar or not. that variable changes in
function visit
and was deleted duplicate of method find_suns_of_vertex