question: boolean removeEdge ( SparseEdge e ) { boolean removedEdge = edges . remove ( e ) ; boolean removedNeighbour = neighbours . remove ( e . getOpposite ( this ) ) ; if ( removedEdge && removedNeighbour ) return true ; else if ( ! removedEdge && ! removedNeighbour ) return false ; else throw new RuntimeException ( "Graph connectivity appears to be inconsitent!" ) ; }
target:  Disconnects this vertex from an edge.