what is hitcounter.py? necessary to call it?

Trying to get a GladeVCP panel to show up in Axis.  The example code in section 9.3.3.5 of the 2.8.2 documentation has a call for hitcounter.py in addition to the UI file defining the panel, but never really explains its inclusion.

Searching the 2.8.2 documentation for that filename comes up with a semi-meaningful hit on page 135 that calls it "a custom python handler".  If required, what should be in it?

When I try to open up LinuxCNC with the attached config (which does not include a callout of hitcounter.py), I get an error that says:

and

Trying to get the homing thing figured out in another thread , but figured this would be a more appropriate place to ask about the GladeVCP part of the error.

Thanks,
David

Found this on github:

github.com/LinuxCNC/linuxcnc/blob/master...gs/sim/hitcounter.py

Well, whatever it is, it's important.  I copied the code from github, dropped it into a new text file in my config folder named hitcounter.py, added the callout for it in my INI file, and now LinuxCNC starts up without error and shows the panel.