ActsTrk::GbtsLayerTool::ReadResult Node1 ActsTrk::GbtsLayerTool ::ReadResult + etaBinWidth   Node2 std::vector< ActsTrk ::GbtsLayerTool::Connection >     Node2->Node1 +connections Node3 ActsTrk::GbtsLayerTool ::Connection + stage + src + dst   Node3->Node2 +elements