Not really a snippet, but if you want to keep track of a buff/debuff on a target that can be applied by more than one person you can use the caster field in the Inspect.Buff.Detail table. To retrieve the player id you can use a self buff that you know the player will use (or for a general addon go through all possible self buffs) and check out the caster field of that buff.
It is kind of a hack and requires the player to use a self buff, but it's better than nothing (at least in my Electrified case). If I don't make sense look in my addon code, although I don't recommend that haha (worse layout than the api documentation
)