case nil => rfl
graph : Graph
start start✝ : Class graph
child : Class.Child start✝
hi : ∀ (h : isCons nil = true), Class.Child.class (split nil h).snd = class nil
h : isCons (cons child nil) = true
⊢ Class.Child.class (split (cons child nil) h).snd = class (cons child nil)
no goals