__init__没有为双重继承类调用

I have the following code:

我有以下代码:

from form_utils import forms as betterforms
from django.db import models

class FilterForm(betterforms.BetterForm):
    def __init__(self, *args, **kwargs):
        super(FilterForm, self).__init__(*args, **kwargs)
        print('filter form __init__')

    ...

class NewEntityForm(FilterForm, FileFormMixin):
    def __init__(self, *args, **kwargs):
        super(NewEntityForm, self).__init__(*args, **kwargs)
        # super(FileFormMixin, self).__init__() <-- really does not matter
        print('newentityform __init__')
from for