It is well know that in (1-)category theory, one can describe the set of natural transformations between two functors by an end formula. I would like to know whether some similar description is available for modifications between two pseudonatural transformations. More precisely:
Let $\mathcal{C}$ and $\mathcal{D}$ be (small) bicategories, $F,G:\mathcal{C}\rightarrow \mathcal{D}$ be pseudofunctors and $a,b:F\Rightarrow G$ be two pseudonatural transformations.
Is there a way to describe the set of modifications from $a$ to $b$ using some end formula?
