/usr/lib/sitesummary/collect.d/siteinfo is in sitesummary-client 0.1.28+deb9u1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 | #!/bin/sh
# site        = location
# sitegroup   = sublocation
# hostclass   = type of host (server, workstation, laptop, etc)
mkdir siteinfo && cd siteinfo
for filename in site sitegroup hostclass ; do
    file=/etc/sitesummary/$filename
    if [ -f $file ] ; then
	cp $file $filename
    fi
done
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