docs: public DataSink<T> setParallelism(int parallelism) {
  		Preconditions.checkArgument(parallelism > 0 || parallelism == ExecutionConfig.PARALLELISM_DEFAULT,
  			"The parallelism of an operator must be at least 1.");
  
  		this.parallelism = parallelism;
  
  		return this;
  	}