How to attach timestamp in DW1001_initiator

Hey, I am trying to attach a timestamp to every tx_message of DW1001_initiator. The role of DW1001_initiator is to transmit messages with timestamps. At the DW1001_responder end, I want to extract the attached timestamp from the message. Could you please tell me which Decawave API function provides the time so that I can attach it to DW1001_initiator messages?