code: public static SlidingWindowAssigner of(Duration size, Duration slide) {
  		return new SlidingWindowAssigner(size.toMillis(), slide.toMillis(), 0, true);
  	}
docs: Creates a new {@code SlidingEventTimeWindows} {@link org.apache.flink.streaming.api.windowing.assigners.WindowAssigner} that assigns
  elements to sliding time windows based on the element timestamp.
  
  @param size  The size of the generated windows.
  @param slide The slide interval of the generated windows.
  @return The time policy.