Nnedi is a new frontline manager at Alphabet. As part of her onboarding, Nnedi has been assigned to meet regularly with Toyin, another manager with many years' experience. Toyin advises Nnedi about Alphabet's culture, protocols, and career paths, as well as the challenges of being a woman of color in a company and industry where men are in the majority. Toyin is probably serving as a(n) _______