4. The method of claim 3 , wherein identifying, as a subset of the set of training images, training images having at least a threshold portion of the identified typical visual features comprises: receiving a score for each image in the set of training images from the low-capacity image relevance model, and identifying images having a score greater than a score threshold as included in the subset of the set of training images.
3. The method of claim 1 , further comprising: training a low-capacity image relevance model based on visual features of the images, the low-capacity image relevance model representing a fixed number of the visual features for the set of training images.