Django update字段在多对多关系中使用表单

from django import forms
from .models import Model1, Model2

class UpdateForm(forms.ModelForm):
    class Meta:
        model = Model1
        fields = ['field1', 'field2', 'model2']

from django.shortcuts import render, get_object_or_404
from .forms import UpdateForm
from .models import Model1

def update_view(request, pk):
    instance = get_object_or_404(Model1, pk=pk)
    form = UpdateForm(request.POST or None, instance=instance)
    
    if form.is_valid():
        form.save()
        # 更新成功后的操作
        
    context = {
        'form': form
    }
    return render(request, 'update.html', context)

<form method="POST">
    {% csrf_token %}
    {{ form.as_p }}
    <button type="submit">更新</button>
</form>