How get inserted row count from Model.insert_many() with postgres?
This is a relatively recent addition:

http://docs.peewee-orm.com/en/latest/peewee/api.html#Insert.as_rowcount

```python
iq = User.insert_many([(u,) for u in ('u1', 'u2', 'u3')])
iq = iq.returning()
assert iq.as_rowcount().execute() == 3
``` I tried it, but not work, I am using postgress and peewee 3.14.10
![image](https://user-images.githubusercontent.com/9300072/173393554-5092c491-5c94-4182-ab62-862c22043f3c.png)

 >This is a relatively recent addition: