checkbox widget not displayed after ajax call in a form by Ajax

I call a form by ajax. In this form, this is a part with a checkbox list. The django widget forms.ModelMultipleChoiceField(queryset= ..., widget=forms.CheckboxSelectMultiple, required=False) not displayed

class AnswerForm(forms.ModelForm):

    skills  = forms.ModelMultipleChoiceField(queryset= Skill.objects.filter(subject_id = 1), widget=forms.CheckboxSelectMultiple, required=False)
    waitings  = forms.ModelMultipleChoiceField(queryset= Waiting.objects.filter(theme__subject_id = 1).order_by("theme"), widget=forms.CheckboxSelectMultiple, required=False)
    knowledges  = forms.ModelMultipleChoiceField(queryset= Knowledge.objects.filter(theme__subject_id = 1 ).order_by("-level").order_by("theme"), widget=forms.CheckboxSelectMultiple, required=False)

    class Meta:
        model = Answer 
        fields = '__all__'

def ajax_create_answer(request):

    id_model = int(request.POST.get('id_model'))
    data = {}  
    form_ans = inlineformset_factory( Item , Answer , fields=('content','right', 'skills','waitings','knowledges',) , extra= 4 )
        print(form_ans)
    template = 'learning/show_vf_multiples.html'

    html = render_to_string(template, context )

    data['html'] = html 
    return JsonResponse(data)

I want the checkbox lists on my form not the default select. Thanks.