{
_runtime += timestep;
ACompositeNode timeStepsNode = new CompositeNode("time tree");
{
VariableNode time = new VariableNode("time");
timeStepsNode.addChild(time);
PhysicalQuantity t = new PhysicalQuantity();
t.setUnit(_timeStepUnit);
}
ATimeSeriesNode leafNode = (ATimeSeriesNode) timeStepsNode.getChildren().get(0);
PhysicalQuantity runTime = new PhysicalQuantity();