how to programmatically set the value for type Deliverable in RTC development,

I got a IDeliverable but to set the values for attribute ,as my attribute id is " com.ibm.team.workitem.attribute.version" which is returning null on calling the findAttribute method .
i have written code below :
IDeliverable deliverable = workItemClient.findDeliverableByName(projectArea, "6.0.0", IDeliverable.DEFAULT_PROFILE, monitor);

IAttribute requestedVersionAttribute = workItemCommon.findAttribute(workItem.getProjectArea(),"com.ibm.team.workitem.attribute.version" , monitor); // returning null here

Now how to set the values for my attribute of type Deliverable.?
attribute id is " com.ibm.team.workitem.attribute.version"