[CentOS] packagekit yumBackend question, perhaps

Periodically I find the yumBackend python script of packagekit really slows
down my CentOS 7 system. I don't invoke anything myself which starts it and
I find nothing in crontab which does either, except perhaps
/etc/cron.hourly/0yum-hourly.cron. But I can't be sure that is the culprit.
I don't find anything at  http://www.freedesktop.org/software/PackageKit
which helps me to debug this. Would someone point me in a useful direction
so that I can find out what /usr/share/PackageKit/helpers/yum/yumBackend.py
is doing, why it is doing it, and how it can be controlled? Many
thanks....Nick