This method is called whenever the node for which this handler is registered is imported or cloned.
DOM applications must not raise exceptions in a UserDataHandler. The effect of throwing exceptions from the handler is DOM implementation dependent.

Parameters:

operation		Specifies the type of operation that is being performed on the node.
key		Specifies the key for which this handler is being called.
data		Specifies the data for which this handler is being called.
src		Specifies the node being cloned, adopted, imported, or renamed. This is null when the node is being deleted.
dst		Specifies the node newly created if any, or null.