The IsPublic method will return 'true' if the special public collection
defined in the ActivityPub spec is addressed in the 'to', 'bto' 'cc', or
'bcc' properties of the Object or any of the types extending from them.
He who fights with monsters should be careful lest he thereby become a monster.
And if thou gaze long into an abyss, the abyss will also gaze into thee.