'Hook for specifying fieldsets for the add form.'

def get_fieldsets(self, request, obj=None):

    if self.declared_fieldsets:
        return self.declared_fieldsets
    form = self.get_form(request, obj)
    fields = (form.base_fields.keys() + list(self.get_readonly_fields(request, obj)))
    return [(None, {'fields': fields})]
