How to add new emails models to email notifications

I tried with:

class Notification(metaclass=PoolMeta):
    __name__ = 'notification.email'

    @classmethod
    def __setup__(cls):
        super().__setup__()
        for field in [
                'recipients',
                'recipients_secondary',
                'recipients_hidden',
                ]:
            field = getattr(cls, field)
            print(field.domain)

But this is the domain defined on the fields:

[('model.model', '=', Eval('model', '')), ['OR', ('relation', 'in', ['res.user', 'party.party', 'party.contact_mechanism', 'company.employee']), [('model.model', 'in', ['res.user', 'party.party', 'party.contact_mechanism', 'company.employee']), ('name', '=', 'id')]], ['OR', ('relation', 'in', ['res.user', 'party.party', 'party.contact_mechanism', 'company.employee', 'company.company']), [('model.model', 'in', ['res.user', 'party.party', 'party.contact_mechanism', 'company.employee', 'company.company']), ('name', '=', 'id')]]]

As you see the relation models are included multiple times, one of them is missing the custom model (company.company) thus the code fails because the domain is applied.