To remove the classmethod, you can use the following code:
```python
try:
  person_id = item[11:] 
except KeyError:
  ...
try:
  assignment_candidate = self.object.assignmentcandidate_set.get(person_id=person_id)
except AssignmentCandidate.DoesNotExist:
  ...
else:
  assignment_candidate.sort_order = data[item]
  assignment_candidate.save()
```