lift a NaturalTransform into a type constructor that has a functor

LiftNaturalTransform.scala

import scalaz._
import scalaz.syntax.functor._

object LiftNaturalTransform {
  def transform[F[_], G[_], M[_]: Functor, A](implicit nt: F ~> G): M[F[A]] => M[G[A]] =
    _ map nt.apply

  implicit class NaturalTransformSyntax[F[_], G[_]](f2g: F ~> G) {
    def lift[M[_]: Functor] =
      new NaturalTransformation[({ type λ[α] = M[F[α]] })#λ, ({ type λ[α] = M[G[α]] })#λ] {
        def apply[A](mf: M[F[A]]): M[G[A]] =
          Functor[M].apply(mf)(f2g)
      }
  }
}