Make grade category optional to avoid error like that:
TypeError: ("'category' must be <class 'vulcan.hebe.data._grade.GradeCategory'> (got None that is a <class 'NoneType'>).", Attribute(name='category', default=NOTHING, validator=<instance_of validator for type <class 'vulcan.hebe.data._grade.GradeCategory'>>, repr=True, eq=True, order=True, hash=None, init=True, metadata=mappingproxy({'key': 'Category'}), type=<class 'vulcan.hebe.data._grade.GradeCategory'>, converter=<related.converters.to_child_field.<locals>.ChildConverter object at 0x7f818b5100>, kw_only=False), <class 'vulcan.hebe.data._grade.GradeCategory'>, None)
Make grade category optional to avoid error like that:
TypeError: ("'category' must be <class 'vulcan.hebe.data._grade.GradeCategory'> (got None that is a <class 'NoneType'>).", Attribute(name='category', default=NOTHING, validator=<instance_of validator for type <class 'vulcan.hebe.data._grade.GradeCategory'>>, repr=True, eq=True, order=True, hash=None, init=True, metadata=mappingproxy({'key': 'Category'}), type=<class 'vulcan.hebe.data._grade.GradeCategory'>, converter=<related.converters.to_child_field.<locals>.ChildConverter object at 0x7f818b5100>, kw_only=False), <class 'vulcan.hebe.data._grade.GradeCategory'>, None)