no goals
V : Type u
V' : Type v
V'' : Type w
G : SimpleGraph V
G' : SimpleGraph V'
G'' : SimpleGraph V''
u v w : V
p : Walk G u v
q : Walk G v w
⊢ Walk.toSubgraph (append p q) = Walk.toSubgraph p ⊔ Walk.toSubgraph q
induction p <;> simp [*, sup_assoc]