I don't think I understand Python Classes and 'self' very well, I'm stuck on another code challenge, can anyone help me?

Hi again, right now I'm learning Python classes and I'm probably not understanding some things. Mostly it's about 'self' and how that sorta thing works. Anyways I got to this coding challenge and this is what it asks me to do.

"Alright, I need you make a new method named 'feedback'. It should take an argument named 'grade'. Methods take arguments just like functions do. You'll still need 'self' in there, though. If 'grade' is above 50, return the result of the 'praise' method. If it's 50 or below, return the 'reassurance' method's result."

I went into my workspace with the code below and everything seems to work. When I run my program nothing pops up in the console unless I add a print function to the return statements of 'praise()' and 'reassurance()', if I do that and test out the 'feedback()' function, it seems to work perfectly fine. If I give the 'feedback' method an argument of 51 or above it will run the 'praise' method, if I give it an argument of 50 or below it will run the 'reassurance' method.

However the code challenge isn't passing me, it's giving me a "NameError" message of some sorts, I tried looking online and how to solve it, tried a few various methods, but nothing seemed to work.

This is the exact error it gave me. "Bummer: Exception: argument of type 'NoneType' is not iterable"

Could anyone help me and show me what I'm doing wrong and maybe give a little insight on how some of this technical Class and 'self' stuff works? Thanks!

class Student:
    name = "TestName"

    def praise(self):
        return "You inspire me, {}".format(self.name)

    def reassurance(self):
        return "Chin up, {}. You'll get it next time!".format(self.name)

    def feedback(self, grade):
        if grade > 50:
            self.praise()
        else:
            self.reassurance()
#end