Function write_10x_matrix 

pub fn write_10x_matrix(
    m: TenxMatrix,
    select_row_type: &str,
    remove_row_type: &str,
    backend_file: &str,
    backend: &SparseIoBackend,
) -> Result<()>

Write m as a new backend at backend_file: rows named {id}_{name} (just id when the name is empty or repeats it; made unique) and kept by type (comma-separated, case-insensitive patterns; a file without types keeps all), columns named as the file names them. Shared by the 10x readers, so every format and entry point names and keeps rows alike.