Fix qtree script
@@ -23,7 +23,7 @@ result = parser.parse(INPUT)
def tree_str(node, depth=0):
indent = ' ' * depth
- if isinstance(node, NodeNonTerm):
+ if node.is_nonterm():
s = '\n{}[.{} {}\n{}]'.format(indent,
node.production.symbol,
''.join([tree_str(n, depth+1)
