simp
case h
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
x a : Node
⊢ a ∈ ↑(direct_succ_list g x).toFinset ↔ a ∈ {y | ∃ ys, y ∈ ys ∧ (x, ys) ∈ g}
case h
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
x a : Node
⊢ a ∈ direct_succ_list g x ↔ ∃ ys, a ∈ ys ∧ (x, ys) ∈ g