How to iter a StructChunked in polars?

Question

I'm working on an extension for the Python Polars library to convert a Struct into JSON. The goal is to use the fields of the struct as the keys and their corresponding values as the JSON values. However, I'm finding it much harder to handle StructChunked than python's pl.struct.

Does anyone have any suggestions or code examples on how to approach this? Any insights or guidance would be greatly appreciated.

Here is my uncompilable code:

use polars::prelude::*;
use pyo3_polars::derive::polars_expr;
use serde_json::*;

#[polars_expr(output_type=Utf8)]
fn to_json(inputs: &[Series]) -> PolarsResult<Series> {
    let ca: &StructChunked = inputs[0].struct_()?;
    let out: Utf8Chunked = ca
        .into_iter()
        .map(|row| serde_json::to_string(row).unwrap())
        .collect();
    Ok(out.into_series())
}