Minor revision about example scripts

[Minys233]

I noticed in example code, some argument are inconsistent in the commented parts, such as lines in examples/molnet/train_molnet.py:

chainer-chemistry/examples/molnet/train_molnet.py

Lines 267 to 274 in 56e83de

	# trainer.extend(ROCAUCEvaluator(
	# valid_iter, predictor, eval_func=predictor,
	# device=args.gpu, converter=concat_mols, name='val',
	# pos_labels=1, ignore_labels=-1, raise_value_error=False))
	#
	# trainer.extend(E.snapshot_object(
	# model, "best_val_" + model_filename[task_type]),
	# trigger=training.triggers.MaxValueTrigger('val/main/roc_auc'))

args.gpu and concat_mols are not consistent with other codes and will throw errors. They should be modified to device and converter, since they are extracted from args or defined in previous lines like this:

chainer-chemistry/examples/molnet/train_molnet.py

Line 209 in 56e83de

device = chainer.get_device(args.device)

chainer-chemistry/examples/molnet/train_molnet.py

Line 233 in 56e83de

converter = converter_method_dict[method]

Since this mistake is too minor to PR, a small issue is enough. Have a nice day :-)

[corochann]

Sorry for confusion for remaining the old legacy code, and thank you for report.