docs: public O 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;
  
  		@SuppressWarnings("unchecked")
  		O returnType = (O) this;
  		return returnType;
  	}