GraphEdges (@NotNull GraphEdges graphEdges) { Set<GraphEdge> edgesInCurrentRow = graphEdges.myEdges; int currentRow = graphEdges.myRow; edgesInCurrentRow.addAll(createUpEdges(currentRow)); edgesInCurrentRow.removeAll(createDownEdges(currentRow - 1)); return new GraphEdges(edgesInCurrentRow, currentRow - 1); }