4): Finally, as in the vanilla Transformer decoder, the third sub-layer is a feed-forward network that processes the representation for the next n+1 layer: The three sources of information (image, object labels, and web entity labels) are treated symmetrically in the above equations.
the only "true" source of information in this case is the image, whereas the other labels are automaticallyproduced annotations that can vary both in quality and other properties (e.g., redundancy).