nostr:npub16pdljvqw3ld0f2mz8mq39tgcvhy3paqmc96kukn9cfscqa29u4wshq3nda One might ask, why not just put the file `submod.rs` inside the `submod` directory (instead of next to it or `mod.rs` inside it)?
Well, that would make having a submodule with the same name (submod::submod) impossible with variant 2! (Not that I would recommend that design)

More importantly, it makes expanding from variant 2 to variant 3 very easy! Or actually, it makes variant 3 only an extension of 2.