@SuppressWarnings("unchecked")
  @Nullable
  public NullabilityProblem<T> asMyProblem(NullabilityProblem<?> problem) {
    return problem != null && problem.myKind == this ? (NullabilityProblem<T>)problem : null;
  }
@SuppressWarnings("unchecked")
  @Nullable
  public NullabilityProblem<T> asMyProblem(NullabilityProblem<?> problem)