7. The method of claim 6 , the training set comprising: a first content item associated with a first reward, and a second content item associated with a second reward that is different from the first reward.
7. The method of claim 6 , the training set comprising: a first content item associated with a first reward, and a second content item associated with a second reward that is different from the first reward. 12. The method of claim 7 , selecting the content items comprising: from the content items having a classification confidence below the classification confidence threshold, selecting the content items associated with the smallest rewards.