intro x a1
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
xs ys : List Node
h1 : xs ⊆ ys
⊢ ∀ x ∈ reachable_from_list g xs, x ∈ reachable_from_list g ys
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
xs ys : List Node
h1 : xs ⊆ ys
x : Node
a1 : x ∈ reachable_from_list g xs
⊢ x ∈ reachable_from_list g ys