Many

			Many(block) <: WrapperBlock

Many indicates that you can variable number of instances for block. Consider a bounding box detection task where there may be any number of targets in an image and this number varies for different samples. The blocks (Image{2}(), BoundingBox{2}() imply that there is exactly one bounding box for every image, which is not the case. Instead you would want to use (Image{2}(), Many(BoundingBox{2}()).