def save_new(self, form, commit=True):
        obj = super().save_new(form, commit)
        getattr(obj, self.m2m.attname).add(self.instance)
        return obj
Saves and returns a new model instance for the given form (single row
dataset/ETHPy150Open allegro/ralph/src/ralph/admin/m2m.py/BaseInlineM2MFormset.save_new