How can I make it so that the form can be used once?

Question

Django

There is a model:

class Model(models.Model):
    . . .
    is_checked = models.BooleanField(default=False)

And in the view:

form = Form(request.POST or None)

    if request.method == 'POST':
        if form.is_valid:
            . . .
            form.save()

How can I make it so that the form can only be used once?