This method is called by a CoordinateSystem (giving this as the first argument) whenever the transform gets attached to it. It tells the transform, ``Hey, I'm attaching you in this direction using this Axis Index List''. This gives the CoordTransform object the chance to update its internal data in a way that is most appropriate to that CoordinateSystem. To do this, the CoordTransform may need retreive data the system's metadata list.
For example, consider our first example of attaching a AbsToRelCoordinateTransform in §3.3.1. In this case, we wanted coordinate positions to be given relative to the system's native reference position. When we attached the transform, the CoordinateSystem determines the constraints for the transform; if they were not given as an argument to attachTransform(), it will call the transform's determineConstraints() method. It then passes the constraints back to the transform via its init() method. Within this method, the transform accesses the values of the ``Axes[n].refposition'' metadata and stores them away to use in its transfromation between absolute and relative coordinates.
The default implementation of the init() method is an empty one; that is, it returns having done nothing. If your transform does not need to update any of its internal data when it is attached to a CoordinateSystem, it is not necessary to override this method.