code: def user_with_ion_id(self, student_id):
          
          if isinstance(student_id, str) and not student_id.isdigit():
              return None
          results = User.objects.filter(id=student_id)
          if len(results) == 1:
              return results.first()
          return None
docs: Get a unique user object by Ion ID. (Ex. 489)