fix a bunch of warnings!

src/line.rs

@@ -7,7 +7,6 @@ use std::num::NonZeroU64;
 #[allow(unused_imports)]
 use crate::prelude::*;
 
-
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Line(pub u64);
 
@@ -43,5 +42,3 @@ impl Line {
         self.0 + 1
     }
 }
-
-pub struct Lines(Vec<Line>);