Open source implementation of "Neural Message Passing for Quantum Chemistry"
(https://arxiv.org/pdf/1704.01212.pdf). Currently only contains the model class
definition and some unit tests. Future release will contain a qm9 dataset reader
and basic trainer.

The default hparams will get reasonable performance on all targets, but the
numbers reported in the paper were done with a separate hyperparameter search
w/ 50 trials on each target.

Disclaimer: This is not an official Google product.