fn fmt(&self, f: &mut Formatter<'_>) -> Result {
        match self {
            Lit::Float(n) => write!(f, "{}", n),
            Lit::Integer(n) => write!(f, "{}", n),
            Lit::String(s) => write!(f, "{}", s),
            // TODO: better representation for Labels
            Lit::Label(n, v) => write!(f, "#{}({})", n, v),
            Lit::Unit => write!(f, "()"),
            Lit::Boolean(b) => {
                write!(f, "{}", if *b { "True" } else { "False" })
            }
        }
    }
Displays some Passerine Data in a pretty manner, as if it were printed
to console.
passerine-common/src/lit.rs