Function read_csv_core 

pub async fn read_csv_core<'a>(
    path_data: &PathData<'a>,
    opts: &OptionSet,
    save_opt: Option<SaveRowFn>,
    out_ref: Option<&str>,
) -> Result<ResultSet, GenericError>

Process a CSV/TSV file asynchronously with an optional row save method and output reference (file or database table reference)