LP-CC1312R7: Observing Resources in CoAP in ti_wisunfan 'ns_coap_node_src' sample app

We would like to subscribe to a CoAP resource on the network using the "Observer" method.

Here's the reference to the IETF reference to rfc7641.

https://datatracker.ietf.org/doc/rfc7641/

How can we send a CoAP Get request with the `Observe` option? Is it possible with the coap_service_request_send() API?

Thanks.