docs: private final AbstractItem _getAndAssertItem() throws SevereMessageStoreException
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(tc, "_getAndAssertItem");
  
          AbstractItem item = null;
          synchronized (this)
          {
              item = _strongReferenceToItem;
          }
  
          // Defect 601995
          if (item == NULL_STRONG_REF)
          {
              if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
                  SibTr.exit(tc, "_getAndAssertItem");
              throw new SevereMessageStoreException("_getAndAssertItem");
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "_getAndAssertItem", item);
          return item;
      }