public MergeObservableList<T> insertItem(T object){
  lists.add(Collections.singletonList(object));
  modCount+=1;
  listeners.notifyInserted(this,size() - 1,1);
  return this;
}

public MergeObservableList < T > insertItem ( T object ) { lists . add ( Collections . singletonList ( object ) ) ; modCount += 1 ; listeners . notifyInserted ( this , size ( ) - 1 , 1 ) ; return this ; }
inserts the given item into the merge list .
