Called as the first operation of swapIdWith 

This function is notified just before an object is to be opened; giving this function the ability to cancel the object being swapped or perform necessary actions. 

When overriding this function: 

1) If the OdDgElement's state is incorrect, throw exception. 

2) Call parent class's subSwapIdWith(). 

3) If other actions are required before swapping IDs, do them. 

The default implementation of this function does nothing. This function can be overridden in custom classes.