Fix small typo in initialisation of exp_y_
Fix small typo in initialisation of exp_y_

CamDavidsonPilon/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers,aitatanit/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers,aitatanit/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers,aitatanit/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers,CamDavidsonPilon/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers,CamDavidsonPilon/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers