modify example to use print function, rather than print statement
diff --git a/examples/explore_ast.py b/examples/explore_ast.py
index 6d3e70c..aaaa9b1 100644
--- a/examples/explore_ast.py
+++ b/examples/explore_ast.py
@@ -143,7 +143,7 @@
 # left and right nodes as children. It also has the op attribute,
 # which is just the string representation of the operator.
 #
-#~ print while_cond.op
+#~ print(while_cond.op)
 #~ while_cond.left.show()
 #~ while_cond.right.show()