POX (software defined network) controller

Question

Python

I decided to test the operation of the POX controller using an example of an existing firewall ( https://openflow.stanford.edu/display/ONL/POX+Wiki#POXWiki-HowdoIcreateafirewall%2FblockTCPports%3F )
But when I try to run the script, I get an IndentationError: expected an indented block
in line
tcpp = event.parsed.find('tcp')