Struggling with Dust API Upsert Document Section Parameter Issues

👋 Browsing the API to upsert document to Dust, I can upload basic text fine, but I'm struggling using the section parameter: Mostly I'm faced with a 400 error telling me that I'm lacking a section prefix, content and sections (?) but I really fail to understand what I'm supposed to add here and it doesn't seem these are part of the documentation? Any pointers?