simplyfy the reading function

src/util.rs

@@ -1,11 +1,11 @@
 use std::fs::File;
-use std::io::{self, BufRead};
+use std::io::{Result, BufRead, BufReader,Lines};
 use std::path::Path;
 
-pub fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+pub fn read_lines<P>(filename: P) -> Result<Lines<BufReader<File>>>
 where
 P: AsRef<Path>,
 {
     let file = File::open(filename)?;
-    Ok(io::BufReader::new(file).lines())
+    Ok(BufReader::new(file).lines())
 }