code: @InterfaceAudience.Public
      public boolean isGone() {
          boolean wasRemovedFromChannel = false;
          Object removed = getProperty("_removed");
          if (removed != null) {
              Boolean removedBoolean = (Boolean) removed;
              wasRemovedFromChannel = removedBoolean.booleanValue();
          }
          return isDeletion() || wasRemovedFromChannel;
      }
docs: Does this revision mark the deletion or removal (from available channels) of its document?
  (In other words, does it have a "_deleted_ or "_removed" property?)