Where to put twisted-theseus profiler?

I am trying to add twisted-theseus profiler to my twisted app.

I run app as following:

/bin/twistd my_app

I putted lines just after app entrypoint:

t = Tracer()
t.install() 
with open('callgrind.theseus', 'wb') as outfile:
    t.write_data(outfile)

Everything that I see in output callgrind.theseus file is:

events: Nanoseconds

What I do wrong?

from Where to put twisted-theseus profiler?