I am retrieving the grading standard id associated with a course via the API. I then use this to match a list of grading schemes I previously read in from canvas. I have noticed however that if a grading standard was deleted I can no longer match it yet if I go into the course in canvas I can see the deleted grading standard still attached to the course. How can I retrieve this grading standard? Or is this historical scheme not retrievable and I just have to make sure the grading schemes are never deleted in the master list?