What is the legal test for penetration past the anal verge to complete the crime of sodomy?

"Sodomy is sexual conduct consisting of contact between the penis of one person and the anus of another person. Any sexual penetration, however slight, is sufficient to complete the crime of sodomy." ( 286, subd. (a).) "[S]odomy requires something more than penetration of the buttocks [citations], but does not require penetration past the anal verge or into the anal canal." (People v. Paz (2017) 10 Cal.App.5th 1023, 1033 (Paz).) "[T]he anal verge connects the end of the anal canal to the anal margin. [Citations.] [] 'The anal margin begins approximately at the anal verge . . . . It represents the transition from the squamous mucosa to the epidermis-lined perianal skin, and extends to the perianal skin.' [Citation.] The outer 'boundary [of the anal margin] is indistinct . . . , and anatomically;' its location varies by person." (Id. at pp. 1034-1035.)