Saves the given intermediate state of the bootstrapping to file.

def _save(self, hdf5, model, positives, negatives):
    """Saves the given intermediate state of the bootstrapping to file."""
    # write the model and the training set indices to the given HDF5 file
    hdf5.set("PositiveIndices", sorted(list(positives)))
    hdf5.set("NegativeIndices", sorted(list(negatives)))
    hdf5.create_group("Model")
    hdf5.cd("Model")
    model.save(hdf5)
    del hdf5