code: func (d Device) AveragePowerUsage(since time.Duration) (uint, error) {
  	if C.nvmlHandle == nil {
  		return 0, errLibraryNotLoaded
  	}
  	lastTs := C.ulonglong(time.Now().Add(-1*since).UnixNano() / 1000)
  	var n C.uint
  	r := C.nvmlDeviceGetAverageUsage(d.dev, C.NVML_TOTAL_POWER_SAMPLES, lastTs, &n)
  	return uint(n), errorString(r)
  }
docs: // AveragePowerUsage returns the power usage for this GPU and its associated circuitry
  // in milliwatts averaged over the samples collected in the last `since` duration.