implemented a primitive tree printing

src/main.rs

@@ -34,7 +34,14 @@ fn main() {
     let root_id = tree.root_node_id();
 
     for x in tree.traverse_pre_order(&root_id.unwrap()).unwrap() {
-        println!("{:?}", x.data());
+        println!("Parent: {:?}", x.data());
+        for y in x.children() {
+            if tree.get(y).unwrap().children().is_empty() {
+                println!("No Children");
+            } else {
+                println!("  Children: {:?}", tree.get(y).unwrap().data());
+            }
+        }
     }
 }