Is there a sample code of a custom workflow approval for mobile app in D365 FO update10?

Hi there,

I'd like to develop a custom workflow and publish the approval forms to mobile app.

I see there is a sample of FleetManagement. https://docs.microsoft.com/en-us/dynamics365/unified-operations/dev-itpro/mobile-apps/platform/mobile-platform-getting-started. However it's different to approval forms.  Is there an instruction of the creation of approval forms for mobile app? (similar to vendor invoice approval)