Function split 

pub fn split<D: Dimension>(
    a: &StringArray<D>,
    sep: &str,
) -> FerrayResult<Vec<Vec<String>>>

Split each string element by the given separator.

Returns a 1-D array where each element is a Vec<String> containing the split parts. This matches NumPy’s behavior where splitting produces a ragged result.

Errors

Returns an error if the internal array construction fails.