Update app.py

app.py

@@ -95,7 +95,7 @@ def create_binary_tree_edges(root):
             new_prev += [child for child in node.children if (len(child.children) > 0)]
         prev = new_prev
 
-    edges
+    return edges
 
 def plot_tree_using_igraph():
     # Define the edges in a tree structure