How to use can_add_related in Django Admin

This is probably coming in late. But for other viewers reference,

def get_form(self, request, obj=None, **kwargs):
    form = super(ProductAdmin, self).get_form(request, obj, **kwargs)
    form.base_fields['category'].widget.can_add_related = False
    return form

can_add_related seems to be an attribute on the widget, not the field, so try:

self.fields['person'].widget.can_add_related = False