simp only [Set.subset_def]
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
xs : List Node
⊢ reachable_from_list g (list_direct_succ_list g xs) ⊆ reachable_from_list g xs
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
xs : List Node
⊢ ∀ x ∈ reachable_from_list g (list_direct_succ_list g xs), x ∈ reachable_from_list g xs