Method _pad

crates/vm/src/builtins/str.rs:1296–1313

(
        &self,
        width: isize,
        fillchar: OptionalArg<PyStrRef>,
        pad: fn(&Wtf8, usize, CodePoint, usize) -> Wtf8Buf,
        vm: &VirtualMachine,
    )

    #[inline]
    fn _pad(
        &self,
        width: isize,
        fillchar: OptionalArg<PyStrRef>,
        pad: fn(&Wtf8, usize, CodePoint, usize) -> Wtf8Buf,
        vm: &VirtualMachine,
    ) -> PyResult<Wtf8Buf> {
        let fillchar = fillchar.map_or(Ok(' '.into()), |ref s| {
            s.as_wtf8().code_points().exactly_one().map_err(|_| {
                vm.new_type_error("The fill character must be exactly one character long")
            })
        })?;
        Ok(if self.len() as isize >= width {
            self.as_wtf8().to_owned()
        } else {
            pad(self.as_wtf8(), width as usize, fillchar, self.len())
        })
    }

    #[pymethod]
    fn center(