1. A data classifier device, comprising: a data storage; and at least one processor configured to predict classification labels for test data by: determining a relationship between the test data and training data, the training data having associated training classification labels, the determining comprising generating a proximity graph in which test data and training data members are represented by nodes of the proximity graph; assigning initial edge weights to the edges between the nodes in the proximity graph that correspond to a similarity between the nodes; performing a first propagation of labels from training data nodes in the proximity graph to test data nodes in the proximity graph based on the initial edge weights; modifying the initial edge weights based on the first propagation of labels; performing a second propagation of labels from training data nodes in the proximity graph to test data nodes in the proximity graph based on the modified edge weights; and adding, after the second propagation of labels, a member of the test data that is part of the proximity graph and its associated label to the training data based on the associated label.