[Python] Polars extract_all get the last item

so this works in polars

path = ['some text 2020', '2021 text 2020', 'etxt 2022', '2023 text 2022']
names = ["Alice", "Bob", "Charlie", "David"]

# Create a Polars DataFrame with columns 'year' and 'name'
df = pl.DataFrame({
"path": path,
"name": names
})

df

year = ['2019', '2020', '2021', '2022', '2023']
pattern = "((?i)" + '|'.join(year) + ")"
df_new = df_new.with_columns(pl.col('path').str.extract(pattern).alias('series'))


But now I want to extract_all and get the last item from the list it returns. This is not working.

year = ['2019', '2020', '2021', '2022', '2023']
pattern = "((?i)" + '|'.join(year) + ")"
df_new = df_new.with_columns(pl.col('path').str.extract_all(pattern).arr.last()).alias('year')


error

SchemaError: invalid series dtype: expected `FixedSizeList`, got `list[str]`


What am I doing wrong? Is .arr.last() wrong?

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