question: @ Override public void enterScope ( final IScope scope ) { super . enterScope ( scope ) ; final ITopology topo = Cast . asTopology ( scope , topology . value ( scope ) ) ; if ( topo != null ) { previous . set ( scope . setTopology ( topo ) ) ; } }
target:  When entering the scope, the statement pushes the topology (if not null) to it and remembers the one that was previously pushed.