How can I create an array from a CSV column encoded as a string using Polars in Rust?

I'm trying to write a Rust program which uses Polars to read a CSV. This particular CSV encodes an array of floats as a string.

In my program, I want to load the CSV into a DataFrame and then parse this column into an array of floats. In Python you might write code that looks like this:

df = pd.read_csv("...")
df["babbage_search"] = df.babbage_search.apply(eval).apply(np.array)

However in my Rust program it's not clear how to go about this. I could take an approach like this:

let mut df = CsvReader::from_path("...")?
    .has_header(true)
    .finish()?;

df.apply("babbage_search", parse_vector)?;

However the parse_vector function is not really clear. I might write something like this, but this won't compile:

fn parse_vector(series: &Series) -> Series {
    series
        .utf8()
        .unwrap()
        .into_iter()
        .map(|opt_v| match opt_v {
            Some(v) => {
                let vec: Vec<f64> = serde_json::from_str(v).unwrap();
                let series: Series = vec.iter().collect();
                series.f64().unwrap().to_owned() as ChunkedArray<Float64Type>
            }

            None => ChunkedArray::<Float64Type>::default(),
        })
        .collect()
}

I'd appreciate any help in figuring this out.