code: protected boolean checkedApply (ObserverOp<T> obop, T obs)
      {
          try {
              return obop.apply(obs);
          } catch (Throwable thrown) {
              log.warning("ObserverOp choked during notification",
                      "op", obop, "obs", observerForLog(obs), thrown);
              // if they booched it, definitely don't remove them
              return true;
          }
      }
docs: Applies the operation to the observer, catching and logging any exceptions thrown in the
  process.