Returns a JSON object describing the occurrence. This is similar to the "Raw JSON" section of the occurrence detail page.

instance_id must be an Occurrence ID for an occurrence in the project. These IDs are returned as the id
field in other occurrence API calls, and can be found in the Rollbar UI on URLs like
https://rollbar.com/Rollbar/demo/items/54/occurrences/3209095494/ (3209095494 is the Occurrence ID).