Need syntax help with Convert Lead API

What's wrong with this call?

headersMap = Map();
headersMap.put("Accept","application/vnd.api+json");
response = invokeurl
[
url :"https://www.zohoapis.com/crm/v3/Leads/4744930000000304421/actions/convert"
type :POST
headers: headersMap
connection:"leads_all"
];

The error message is:

{"code":"INVALID_DATA","details":{"expected_data_type":"jsonobject"},"message":"body","status":"error"}

The error message hints at the notion that that one or more parameters are missing.

The documentation here hints at the notion that all parameters are optional.

Convert Lead - APIs | Online Help - Zoho CRM

Zoho Team,

I want you to know that I always try to self-serve by using your documentation. The single biggest thing that would help me is to offer complete, Deluge-based examples. The support I get here is pretty good (and some people are outstanding) and still, I now wait for an answer and my progress is stopped until I hear from you. Please. Please. Please.