public static @NotNull Nullability inferLambdaNullability(PsiLambdaExpression lambda) {
    if (LambdaUtil.getFunctionalInterfaceReturnType(lambda) == null) {
      return Nullability.UNKNOWN;
    }

    return inferBlockNullability(lambda, false);
  }
public static @NotNull Nullability inferLambdaNullability(PsiLambdaExpression lambda)