What is the 'image' attribute for a HumanUser. All the docs talk about for images is pertaining to versions/attachments. The docs also say 'image' is a string url which makes sense. But if I ask for 'image' in the return fields of a HumanUser I get back an number. I assumed image would be a url to the users thumbnail for their profile. How can I access the users thumbnail for their profile from the api.