how to checkout the workspace object through api

private void addToWorkspace(EPMDocument doc) {

try {

wt.fc.ReferenceFactory referencefactory = new wt.fc.ReferenceFactory();

wt.fc.WTReference wtreference = referencefactory.getReference(doc);

wt.epm.EPMDocument epm = (wt.epm.EPMDocument) wtreference.getObject();

System.out.println("epm-->"+epm);

wtreference = referencefactory.getReference("OR:wt.epm.workspaces.EPMWorkspace:1150900");

wt.epm.workspaces.EPMWorkspace workspace= (wt.epm.workspaces.EPMWorkspace) wtreference.getObject();

System.out.println("workspace-->"+workspace);

//Get the EPMDocument configuration

wt.epm.workspaces.EPMAsStoredConfigSpec asStored = wt.epm.workspaces.EPMAsStoredConfigSpec.newEPMAsStoredConfigSpec(epm);

wt.fc.QueryResult queryResult = wt.epm.structure.EPMStructureHelper.service.navigateReferencesToIteration(epm, null, true, asStored);

//To add to workspace, set some collection

wt.fc.collections.WTHashSet collection = new wt.fc.collections.WTHashSet();

collection.add(epm);

// Add to workspace

wt.epm.workspaces.EPMWorkspaceHelper.manager.addToWorkspace(workspace, collection);

//Get check out folder for the current user in the session

wt.folder.Folder checkoutFolder1 = wt.vc.wip.WorkInProgressHelper.service.getCheckoutFolder();

//Check out object

wt.vc.wip.CheckoutLink chklink1 = wt.vc.wip.WorkInProgressHelper.service.checkout(epm, checkoutFolder1, "Check out comment");

wt.epm.EPMDocument wrk1 = (wt.epm.EPMDocument) chklink1.getWorkingCopy();

} catch (WTException | WTPropertyVetoException e) {

e.printStackTrace();

}

}

 this is coming like this, i wanted to checkout from workspace