Convert an Eigen3 Transform's rotation into an AngleAxis

Question

How can this be done using Eigen 3?

#include <Eigen/Geometry>

Affine3d transform;
AngleAxisd aa = ...;

Answer 1

Of course, I found the answer shortly after posting the question.

Affine3d transform;
AngleAxisd aa(transform.rotation());

Naturally this discards any translation component in the original affine transformation.