Function inner_join_csv 

pub fn inner_join_csv(
    left: &CsvFile,
    right: &CsvFile,
    key: &str,
) -> Result<CsvFile, String>

Inner-join two CsvFiles on a shared key column.

Rows are matched when the key column value is equal (string comparison). The output contains all columns from left followed by the non-key columns of right.