How to correctly write the required parameter attachment in the mediatopic.post OK API request?

Question

API

Using the API, I'm trying to set up user status in Odnoklassniki. The mediatopic.post request has a required attachment parameter . Based on the documentation, I do not quite understand what I should (and how) should oversleep into this request parameter. The documentation says JSON-encoded information about the content of the media topic
Who figured it out - please tell me.