  Given a Hopf algebra in a symmetric monoidal category with duals, the
category of modules inherits the structure of a monoidal category with duals.
If the notion of algebra is replaced with that of monad on a monoidal category
with duals then Bruguieres and Virelizier showed when the category of modules
inherits this structure of being monoidal with duals, and this gave rise to
what they called a Hopf monad. In this paper it is shown that there are good
diagrammatic descriptions of dinatural transformations which allows the
three-dimensional, object-free nature of their constructions to become
apparent.
