code: private final void setInMemoryItemSize(AbstractItem item)
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "setInMemoryItemSize", item);
          // If we have an Item, we can ask it for its estimated size.
          if (item != null) {
              _inMemoryItemSize = item.getInMemoryDataSize();
          }
          // Otherwise, we just use its persisted size & our standard multiplier.
          else {
              _inMemoryItemSize = _tuple.getPersistentSize() * MEMORY_SIZE_MULTIPLIER;
          }
          // Set the value on the Tuple.
          _tuple.setInMemoryByteSize(_inMemoryItemSize);
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "setInMemoryItemSize", _inMemoryItemSize);
      }
docs: setInMemoryItemSize
  Set the _inMemoryItemSize from the Item itself, if we have one, or from what
  we can find out from the Tuple. Also set the corresponding value in the Tuple.