understand the grid_pad for affine distribution

[todo]

rising/rising/transforms/functional/pad.py

Lines 27 to 32 in 3210713

	# todo: understand the grid_pad for affine distribution
	if grid_pad is False:
	return F.pad(data, pad=pad_size, mode=mode, value=value)
	else:
	raise NotImplementedError(grid_pad)

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This issue was generated by todo based on a todo comment in 3210713 when #9 was merged. cc @jizongFox.