StoreRegistryEntries Augmentation

I'm finding it a little difficult understanding how to augment the interface, specifically the commands store because I have my own extended class from sapphire's Command, and I keep having to do
as <Class>
as <Class>
whenever I retrieve a command from
container.stores.get('commands').get(commandName)
container.stores.get('commands').get(commandName)
.

~~How am I supposed to do it?~~

Scrap the above. From what I can see each store is stronly typed and a new type can't be assigned. This would be confirmed when looking at skyra's codebase too because types are manually casted.