Expressified `expr.name.map` about polars HOT 2 OPEN

def expr_fn_to_str_fn(f: Callable[[pl.Expr], pl.Expr]) -> Callable[[str], str]:
    return lambda s: pl.select(f(pl.lit(s))).item()

def to_canonical_ident(expr: pl.Expr) -> pl.Expr:
    return (
        expr.str.replace_all(r"[^\w]", "_")
        .str.replace_all(r"__+", "_")
        .str.to_lowercase()
    )

expr.name.map(expr_fn_to_str_fn(to_canonical_ident))