Lean4
/-- A Lie algebra `L` is said to be Engelian if a sufficient condition for any `L`-Lie module `M` to
be nilpotent is that the image of the map `L → End(M)` consists of nilpotent elements.
Engel's theorem `LieAlgebra.isEngelian_of_isNoetherian` states that any Noetherian Lie algebra is
Engelian. -/
def IsEngelian : Prop :=
∀ (M : Type u₄) [AddCommGroup M] [Module R M] [LieRingModule L M] [LieModule R L M],
(∀ x : L, IsNilpotent (toEnd R L M x)) → LieModule.IsNilpotent L M