How to show text on 'PREVIEW' mode of video sequencer, instead of 'SEQUENCER'?

How do I get this text to show up in Preview mode instead of video sequencer mode? I swear it’s probably just a small change in line 19, but I can’t find a way to specify ‘PREVIEW’ instead of the default ‘SEQUENCER’ in the type. Can somebody help me out?

I am A little confuse with the question, do you mind to give a more detailed explanation?