Confusion in using lighting batch transforms

I am confused by usage of lighting transforms. For example:

img = PILImage.create(filename)
timg = TensorImage(array(img)).permute(2,0,1).float()/255.

batch_tfms = Brightness(p=1, draw=[0.9])
tim1 = batch_tfms(timg[None])[0]
tim2 = timg[None].brightness(p=1, draw=[0.9])[0]


The two images should be the same, but tim1 doesn’t show any brightness change while tim2 always show (as it should be).

I also noticed for affine and coord transforms, both two images change. For example, if I replace the Brightness to Rotate in the example above, both images are rotated.

Does anybody know why is this?