How to revise WTPartDescribeLink?

I have a WTPart object and it have some Describe link(as WTDocument) associated with it.Now I need to revise the describe link through code.

Following is the code I have tried so far

Vector localVector=new Vector();
   QueryResult localQueryResult=WTPartHelper.service.getDescribedByWTDocuments(part,false);
    System.out.println("size is "+localQueryResult.size());
    if((localQueryResult!=null)&&(localQueryResult.hasMoreElements()))
    {
        while(localQueryResult.hasMoreElements())
        {
               WTObject localObject=(WTObject) localQueryResult.nextElement();
           localVector.addElement(localObject);
        }
    }
    if((localVector!=null)&&(localVector.size()>0))
    {
        for(int i=0;i<localVector.size();i++)
        {
            WTPartDescribeLink localPartlink=(WTPartDescribeLink) localVector.elementAt(i);
            WTDocument localWTDocument=localPartlink.getDescribedBy();
            System.out.println("values are "+localWTDocument.getNumber());
            RevisionControlled localRevisionControlled=null;
            localRevisionControlled=(RevisionControlled) VersionControlHelper.service.newVersion(localWTDocument);
            localRevisionControlled=(RevisionControlled) PersistenceHelper.manager.save(localRevisionControlled);

        }
    }

This code is revising only the WTDocument object which is linked as Describelink but not revising the Describelink. If I pass the Describe link object directly like this

localRevisionControlled=(RevisionControlled) VersionControlHelper.service.newVersion((Versioned)localPartlink);

means I'm getting error message like following

Exception in thread "main" java.lang.ClassCastException: wt.part.WTPartDescribeLink cannot be cast to wt.vc.Versioned
    at ext.gt.test.CheckLink.getPartlink(CheckLink.java:100)
    at ext.gt.test.CheckLink.searchPart(CheckLink.java:52)
    at ext.gt.test.CheckLink.main(CheckLink.java:32)

I don't know how to solve this issue but I need to revise the Part describelink by code.Suggest me the API which is needed for this or some example code snippet would be useful for me.

Solution

According to the answer given above by @Julien Boulay ,I have created a method which query the the document object and then revise that document after I have created a new link with my part.

private WTPartDescribeLink getPartlink(WTPart target) throws WTException, WTPropertyVetoException {
        WTDocument localWTDocument=null;
        if(target==null)
            return null;
        QueryResult localQueryResult=WTPartHelper.service.getDescribedByWTDocuments(target, false);
        ilogger.info("size of query result is "+localQueryResult.size());
        if((localQueryResult!=null)&&(localQueryResult.hasMoreElements()))
        {
            while(localQueryResult.hasMoreElements())
            {

                 WTObject localObject=(WTObject) localQueryResult.nextElement();
                 WTPartDescribeLink localPartlink=(WTPartDescribeLink) localObject;
                 localWTDocument=localPartlink.getDescribedBy();
            }
        }

        WTDocument docm=(WTDocument) VersionControlHelper.service.allVersionsOf(localWTDocument).nextElement();
        ilogger.info("values are "+docm.getNumber());
        String version=docm.getVersionIdentifier().getValue();
        String iteration=docm.getIterationIdentifier().getValue();
        ilogger.info("Object passing with version and iteration of"+version+"."+iteration);
        RevisionControlled localRevisionControlled=null;
        localRevisionControlled=(RevisionControlled) VersionControlHelper.service.newVersion(docm);
        localRevisionControlled=(RevisionControlled) PersistenceHelper.manager.save(localRevisionControlled);
        createLink(target,docm);
        return null;
    }

    private void createLink(WTPart spart, WTDocument localWTDocument) throws WTException {

                WTPartDescribeLink link=WTPartDescribeLink.newWTPartDescribeLink(spart, localWTDocument);
                PersistenceServerHelper.manager.insert(link);
                ilogger.info("Link saved ");

        }

The above code is now works fine.