The generated test cases for the linked list seem to be wrong, because the added nodes are stored in reverse order (the last element added is the first list element), and according to the tests the last element added should be the last element in the list.
I tested that with the lines
list1 = create_linked_list([“Mon”, “Tue”, “Wed”])
print(list1.dataval, list1.nextval.dataval, list1.nextval.nextval.dataval)
and got the output
Wed Tue Mon