Allow_none in additional parameters

[RedekG]

Hi!

Is it possible that additional attributes have null value? If so how to set it?
Here is an example of a code:

class Test(Schema):
    class Meta:
        include = {
            "tester:test": fields.Str(),
        }
        additional = ["test:one","test:two","test:three"]
        ordered = True

[lafrech]

I don't think this is possible and I don't think it will change.

We want to deprecate/remove the additional feature (#1356).