How to create a capped collection from odmantic ?

[aahnik]

For my application, I have some global configuration, which I want to persist in my database.

The model definition is something like this

class AdminConfig(Model):
    blah_val: int = 10
    foo:str = "bar"
    spam:List[int] = [1,2]

Now, I want only one instance of the class to exist. Thus, there will be only one document in the AdminConfig collection, at a point in time.

I think using a capped collection is the way to go, so that only one document is allowed.

In the model definition, is there a way to define before hand, that the cap is one instance ?

[aahnik]

Currently, I am using a naive workaround, to ensure only one instance of the class.

I added a primary key, that will contain the value 1 always.

class AdminConfig(Model):
    one_id:int = Field(primary_field=True)
    # blah blah

Now to access the document, I am using the one_id=1

admin_cfg = await engine.find_one(AdminConfig,AdminConfig.one_id==1)
if not admin_cfg:
    admin_cfg = await engine.save(AdminConfig(one_id=1))
admin_cfg: AdminConfig

Is there a more mature or standard way of achieving what I am trying to do ?