Insert returning using :one has nullable return type

[anuraaga]

When defining an insert statement with a returning, using :one, the generated return type of the method has | None attached to it. AFAIK, the only possibilities are to get a result or to have an exception when inserting a statement, and presumably the | None is added automatically as it's how :one is normally generated. Is it possible to generate a different return type for :one when it is an INSERT statement?