if you add multiplication functionality, identity and termination symbols to it, you get something that is closer to a proper category like done in this: https://github.com/kummahiih/python-category-equations

f1(?) |> ( f2(?), I ) |> f3(?) == f1(?) |> f2(?) |> f3(?) , f1(?) |> f3(?)

it just feels natural that way