…thState followup

### What changes were proposed in this pull request?

This is a followup of #38013 which introduce an example for applyInPandasWithState. Address some comments on code style.

Closes #38066 from chaoqin-li1123/example_followup.

Authored-by: Chaoqin Li <chaoqin.li@databricks.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>