/** Creates the inverse transform of this object. */
 @Override
 public MathTransform inverse() {
   if (inverse == null) {
     inverse =
         new MolodenskiTransform(
             abridged, a + da, b + db, target3D, a, b, source3D, -dx, -dy, -dz);
     inverse.inverse = this;
   }
   return inverse;
 }