Before revision:  Second, we present a randomized stochastic method for non-convex SBO with m>1 lower level problems by processing only one lower problem at each iteration, and establish its sample complexity no worse than O(m/\epsilon^3), which could have a better complexity than  simply processing all m lower problems at each iteration.
After revision:  Second, we present a randomized stochastic method for non-convex SBO with m>1 lower level problems by processing only one lower problem at each iteration, and establish its sample complexity no worse than O(m/\epsilon^3), which could be a better complexity than simply processing all m lower problems at each iteration.