Accessibility API for Math Expression on iOS

My app have raw MathML expression that I'd like to pass to iOS Accessibility framework, so ideally user can use rotor to change granularity when using VoiceOver (such as small/medium/large expressions) to navigate within the equation. This example shows the experience that I am aiming for in Apple Books: https://www.perkins.org/resource/how-read-math-expressions-voiceover-ios-device/.

However, I couldn't find what's the best way to expose the raw MathML expression to the accessibility framework. AFAIK, the only way to pass accessibility information to iOS Accessibility framework is by setting the attributes, including label, value, traits, hint, etc. But by experimenting with them, I couldn't get VoiceView to allow the small/medium/large expressions in the rotor.

Is there a way to pass raw MathML expression to iOS accessibility framework?

Thanks.