code: func (d Device) PowerUsage() (uint, error) {
  	if C.nvmlHandle == nil {
  		return 0, errLibraryNotLoaded
  	}
  	var n C.uint
  	r := C.nvmlDeviceGetPowerUsage(d.dev, &n)
  	return uint(n), errorString(r)
  }
docs: // PowerUsage returns the power usage for this GPU and its associated circuitry
  // in milliwatts. The reading is accurate to within +/- 5% of current power draw.