No, we don't want to use that.  The `applyLensing` function is pretty simple:
```
self.applyShear(g1=g1, g2=g2)
self.applyMagnification(mu)
```
So the only difference between that and what we are doing here is that applyLensing is not flux-conserving.  We want `_profileToWorld` to conserve flux, so `applyLensing` does the wrong thing.