Bluey Beacon Main loop

Bluey Beacon Main loop.c

int main(void)
{
    uint32_t err_code;

    APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);

    ble_stack_init();
    advertising_init();
    timers_init();
    advertising_start();
    application_timers_start();
    
    twi_init();
    HDC1010_init(TEMP_OR_HUMID);
    APDS9301_init();

    // Enter main loop.
    for (;; )
    {
      // one-shot flag to set adv data
      if(g_setAdvData) {
        set_adv_data(false);
        g_setAdvData = false;
      }

      power_manage();
    }
}

Can I find the definition of application_timers_start();
I am unable to go to beacon_timeout_handler() function