Method for UART receive data in provided UART DTM project in BlueNRG SDK

[SBukh.1]

Using the DTM UART project "BlueNRG-1_2 DK 3.1.0/Project/BLE_Examples/DTM" there is a method to send data (transport_layer_send_data) available. However, the corresponding transport_layer_receive_data logic is blocked out by #ifdef and appears to only be available if using SPI as the communication method.

Is anyone familiar with what logic the UART DTM uses to receive data over UART?