question: @ Override public Set < Statement > apply ( final IGASState < Set < Statement > , Set < Statement > , Set < Statement > > state , final Value u , final Set < Statement > sum ) { if ( sum != null ) { final Set < Statement > us = state . getState ( u ) ; us . addAll ( sum ) ; return us ; } return null ; }
target:  UNION the gathered edges with those already decorating the vertex.