Revisit the need for _ModelMetaclass hack in pydantic v2

[github-actions]

omnipy/src/omnipy/data/model.py

Line 99 in 86e1ee9

# TODO: Revisit the need for _ModelMetaclass hack in pydantic v2

    # subfields, e.g. in `list[MyModel]` as `get_origin(MyModel) is None`. Here, we want allow_none
    # to be set to True so that Model is allowed to validate a None value.
    #
    # TODO: Revisit the need for _ModelMetaclass hack in pydantic v2
    def __instancecheck__(self, instance: Any) -> bool:
        if instance is None:
            return True
        return super().__instancecheck__(instance)


class Model(GenericModel, Generic[_RootT], DataClassBase, metaclass=_ModelMetaclass):
    """
    A data model containing a value parsed according to the model.