mathlib3

d5c58eb8 - chore(category_theory/*): make all forgetful functors use explicit arguments (#4139)

chore(category_theory/*): make all forgetful functors use explicit arguments (#4139) As suggested as https://github.com/leanprover-community/mathlib/pull/4131#discussion_r487527599, for the sake of more uniform API. Co-authored-by: Scott Morrison <scott.morrison@gmail.com>