AttributeError: 'ModelName' object has no attribute 'save_m2m'

[Anjaneyulu]

instance = form.save(commit=False)
instance.updated_by = self.request.user
instance.save()
instance.save_m2m()

I'm getting below error. Django version 1.11.6

AttributeError: 'ModelName' object has no attribute 'save_m2m'

But in documentation ​https://docs.djangoproject.com/en/1.11/topics/forms/modelforms/

every time you save a form using commit=False, Django adds a save_m2m() method to your ModelForm subclass. After you’ve manually saved the instance produced by the form, you can invoke save_m2m() to save the many-to-many form data.

[Tim Graham]

You need to use form.save_m2m() rather than instance.save_m2m().