Rust stripMargin

strip_margin.rs

pub trait StripMargin {
    fn strip_margin(self) -> String;
}

impl StripMargin for &'static str {
    fn strip_margin(self) -> String {
        let mut out = Vec::new();
        for l in self.lines()
            .filter(|x| !x.is_empty() ) {
            for s in l.splitn(2, '|').nth(1) {
                out.push(s);
            }
        }
        out.join("\n")
    }
}

Hi,
I have this error, could you help me what there is wrong?

You cannot call a method on a null-valued expression.
At C:\Users\crizzo\Desktop\beta\New folder (2)\credici.ps1:29 char:1

• $xtw.dispose()

•   + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull