Function try_open_or_convert 

pub fn try_open_or_convert(
    data_file: &str,
) -> Result<Box<dyn SparseIo<IndexIter = Vec<usize>>>>

Try to open a data file directly; if that fails, attempt automatic conversion from raw 10x formats (h5/h5ad, zarr/zarr.zip).

Converted backends are cached as {data_file}.db.zarr next to the original file so subsequent calls skip conversion.