“assault by penetration” is when a person (A)
(a) intentionally penetrates the vagina or anus of another person (B) with a part of their body or anything else,
(b) the penetration is sexual,
(c) and B does not give lawful consent to the penetration, and A does not reasonably believe that B gave lawful consent.
Whether a belief is reasonable is to be determined having regard to all the circumstances, including any steps A has taken to ascertain whether B gave lawful consent.