Cannot custom _id

[veerkat]

I try to custom _id, like this:

User.objects.create(_id=1, name="veerkat")

but it failed.
Because objects.create call QuerySet.create

@return_future
def create(self, callback, alias=None, **kwargs):
    document = self.__klass__(**kwargs)
    self.save(document=document, callback=callback, alias=alias)

def save(self, document, callback, alias=None):
    if self.validate_document(document):
        self.ensure_index(callback=self.indexes_saved_before_save(document, callback, alias=alias), alias=alias)

def indexes_saved_before_save(self, document, callback, alias=None):
    def handle(*args, **kw):
        self.update_field_on_save_values(document, document._id is not None)
        doc = document.to_son()

        if document._id is not None:
            self.coll(alias).update({'_id': document._id}, doc, callback=self.handle_update(document, callback))
        else:
            self.coll(alias).insert(doc, callback=self.handle_save(document, callback))

    return handle

and create method call save method. But in indexes_saved_before_save method, if document._id is not None, it will call update method, and cannot create an new instance.