Shouldn’t this call `MagickNormalizeImageChannel(MagickWand *wand, const ChannelType channel)` or remove second argument to satisfy the interface of `MagickNormalizeImage(MagickWand *wand)`?

<http://www.imagemagick.org/api/magick-image.php#MagickNormalizeImage>

It would be better if the default value of `channel` is `None` and it conditionally calls `MagickNormalizeImageChannel()` or `MagickNormalizeImage()`.