Update app.py

app.py

@@ -25,7 +25,7 @@ def genFlatDepthTree(expr):
     def tree(tk, last_node, depth):
         if tk.n_lefts + tk.n_rights > 0:
             for ch in tk.children:
-                tree(ch, Node(ch.text+"\t"+postag(ch)++" - ["str(depth+1)+"]", parent=last_node), depth+1)
+                tree(ch, Node(ch.text+"\t"+postag(ch)+" - ["+str(depth+1)+"]", parent=last_node), depth+1)
     
     tree(root, node, 0)
     flat_tree = ""