Function ensure_rust_extractor_registered 

pub fn ensure_rust_extractor_registered<T>() -> Result<(), Error>
where
    T: CustomDataTrait + for<'a, 'py> FromPyObject<'a, 'py> + Send + Sync + 'static,

Registers a Rust custom data type for Python extraction if not already registered. If the type is already registered, returns Ok(()) without overwriting (idempotent). Use this where repeated registration can occur (e.g. module load).

Errors

Does not return an error (idempotent insert into DashMap).