Nested JSON and HttpSMSProvider

When I choose SEND_DATA_AS_JSON “yes” while creating SMS Gateway:
Config - SMS Gateways - Create new SMS Gateway definition - ProviderModule “HttpSMSProvider” - SEND_DATA_AS_JSON “yes”
I whould like to add the following json which has included additional level with “body” item. Is it possible to do? I can’t find how to do it.
json data:
“chat_id”: “id”,
“notification”: {
“body”: “text”