data: {111: {'sends': 1000, 'open_rate': 0.11}, 112: {'sends': 1000, 'open_rate': 0.13}, 113: {'sends': 1000, 'open_rate': 0.16}}
key - subject_id sends - count has sent emails open_rate - conversion opened/sends
use bandit to optimize open_raye between subject_id Bernoulli probability for each arm equal to open_dare