code: @SuppressWarnings("unchecked")
  	@Override 
  	public boolean contains(Object o) {
  		if (elements instanceof List<?>) {
  			try {
  				return Collections.binarySearch((List<T>) elements, (T) o) >= 0;
  			} catch (ClassCastException e) {
  				return false;
  			}
  		}
  		return elements.contains(o);
  	}
docs: {@inheritDoc}