[Ahman et al.][1] wrote about when a container is a comonad. Containers can also be monads, such as List.  This means that we can take all containers that are endofunctors on Set and they live in the endofunctor category on set.  This category has a monoidal product, which is functor composition.  Thus we can have a monoidal category for containers that are either monads or comonads.  This must have a diagrammatic calculus.  What are the axioms of this diagrammatic calculus?



  [1]: https://arxiv.org/abs/1408.5809 "Ahman et al."