code: public static <T, W extends Window> DeltaTrigger<T, W> of(double threshold, DeltaFunction<T> deltaFunction, TypeSerializer<T> stateSerializer) {
  		return new DeltaTrigger<>(threshold, deltaFunction, stateSerializer);
  	}
docs: Creates a delta trigger from the given threshold and {@code DeltaFunction}.
  
  @param threshold The threshold at which to trigger.
  @param deltaFunction The delta function to use
  @param stateSerializer TypeSerializer for the data elements.
  
  @param <T> The type of elements on which this trigger can operate.
  @param <W> The type of {@link Window Windows} on which this trigger can operate.