This model is used to predict fitness of GB1 protein variants.
Nicholas C Wu, Lei Dai, C Anders Olson, James O Lloyd-Smith, Ren Sun (2016) Adaptation in protein fitness landscapes is facilitated by indirect paths eLife 5:e16965
https://doi.org/10.7554/eLife.16965
Label is the fitness of mutant protein. The fitness of each variant can be viewed as the fitness relative to wildtype,
such that = 1. Therefore all labels are larger than 0, if label >1 means high fitness compare to wildtype.