The python example is (also) used to test the feature. That is because
currently nmcli does not yet have support for ovs.external-ids and this
API is only accessible via D-Bus (or a tool like this example).
And example script for getting and setting OVS external-ids.
Since currently there is no nmcli support for these properties yet,
the script becomes more interesting.
This "example" is rather long, and it showcases less the usage of
libnm (which is rather trivial, with respect to configuring
NMSettingOvsExternalIDs). Instead, it aims to provide a useful
command line tool for debugging. Hence, it's mostly concerned with
an elaborate command line syntax and useful print output.
