* Unbinds event handlers for either all of an [Item]'s gossip events, or one type of event. * * If `event_type` is `nil`, all the [Item]'s gossip event handlers are cleared. * * Otherwise, only event handlers for `event_type` are cleared. * * **NOTE:** this will affect all instances of the [Item], not just one. * To bind and unbind gossip events to a single [Item
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