How to get input and output variable names in the Human Task?

Issue

How to get input and output task variable names in the On Entry / Exit method?

Following code kind of worked for input parameters:

HumanTaskNodeInstance nodeInstance = (HumanTaskNodeInstance) kcontext.getNodeInstance();
HumanTaskNode humanTaskNode = (HumanTaskNode) nodeInstance.getHumanTaskNode();
WorkImpl workImpl = (WorkImpl) humanTaskNode.getWork();
Map inputparams = workImpl.getParameters();

but there is no method to get results object (output parameter names)