simp only [list_direct_succ_set]
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
x : Node
xs : List Node
⊢ list_direct_succ_set g (x :: xs) = ↑(direct_succ_list g x).toFinset ∪ list_direct_succ_set g xs
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
x : Node
xs : List Node
⊢ {y | ∃ x_1 ∈ x :: xs, ∃ ys, y ∈ ys ∧ (x_1, ys) ∈ g} =
    ↑(direct_succ_list g x).toFinset ∪ {y | ∃ x ∈ xs, ∃ ys, y ∈ ys ∧ (x, ys) ∈ g}