docs: private O setResources(ResourceSpec resources) {
  		Preconditions.checkNotNull(resources, "The resources must be not null.");
  		Preconditions.checkArgument(resources.isValid(), "The values in resources must be not less than 0.");
  
  		this.minResources = resources;
  		this.preferredResources = resources;
  
  		@SuppressWarnings("unchecked")
  		O returnType = (O) this;
  		return returnType;
  	}