public ThreadGroupReferenceProxyImpl parent() {
    checkValid();
    if (!myIsParentGroupCached) {
      myParentThreadGroupProxy = getVirtualMachineProxy().getThreadGroupReferenceProxy(getThreadGroupReference().parent());
      myIsParentGroupCached = true;
    }
    return myParentThreadGroupProxy;
  }
public ThreadGroupReferenceProxyImpl parent()