Return run counts only for examples that are still correctly classified

def filter(self, run_counts, criteria):
    """
    Return run counts only for examples that are still correctly classified
    """
    correctness = criteria['correctness']
    assert correctness.dtype == np.bool
    filtered_counts = deep_copy(run_counts)
    for key in filtered_counts:
      filtered_counts[key] = filtered_counts[key][correctness]
    return filtered_counts