Use of children count and simple error handling

src/node/mod.rs

@@ -12,10 +12,15 @@ pub struct Node {
 }
 
 impl Node {
-    pub fn new(children: Option<Vec<Node>>, handler: NodeHandler) -> Self {
+    pub fn new(
+        children: Option<Vec<Node>>,
+        handler: NodeHandler,
+        max_children_count: Option<usize>,
+    ) -> Self {
         Self {
             children: children.unwrap_or(vec![]),
             handler: handler,
+            max_children_count,
         }
     }
     pub fn get_value(&self) -> f64 {