Django ModelAdmin "Save as New"

save_as_new.py

class MyModelAdminForm(forms.ModelForm):
    '''
    To add the option 'Save as New', by default does not work for reverse
    ManyToMany/ForeignKey fields. In other words, does not copy over the 
    reverse attributes. A simple workaround to make this happen is:
    update the cleaned_data and returning it in the context.
    Something like this:
    '''
    def clean(self, *args, **kwargs):
        cd = self.cleaned_data
        if self.request.method == 'POST' and '_saveasnew' in self.request.POST:
            #Lets say the slug attribute is unique:
            name = cd.get('name', '')
            slug = cd.get('slug', '')
            slug_exists = Campaign.objects.filter(slug=slug).exists()

            while slug_exists:
                name = name + ' Copy'
                slug = slug + '-copy'
                slug_exists = Campaign.objects.filter(slug=slug).exists()

            cd.update({'name': name, 'slug': slug})
        return cd

    class Meta:
        model = MyModel