Monochrom labels

Is there an easy way to force loading depth maps (uint16) as monochorome without default PIL rgb conversion in databunch?

If any 1 needed I resolved it as fallows:
src.label_from_func(lambda x: path_gt+’/depth’[3:-3]+‘tiff’, convert_mode = None)
and then in custom loss divide by 255 (as images are divided by 255 by standard and here we have maximum of 255*255)