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