unfold joinF.associatorLeft
α : Type u
inst✝ : Category α
asss : List (List (List α))
⊢ joinF.associatorLeft ([] :: asss) = joinF.associatorLeft asss
α : Type u
inst✝ : Category α
asss : List (List (List α))
⊢ associatorLeft.aux [] [] ([] :: asss) = associatorLeft.aux [] [] asss