docs: public void setParallelism(int parallelism) {
  		Preconditions.checkArgument(
  				parallelism > 0 || parallelism == ExecutionConfig.PARALLELISM_DEFAULT,
  				"The parallelism must be at least one, or ExecutionConfig.PARALLELISM_DEFAULT (use system default).");
  		this.parallelism = parallelism;
  	}