Implement a fixed energy logic for the xrt lens. These are put in based on the photon energy and are not part of the focus optimization. However, they should be accounted for in the focus calculation with the TFS lenses. This is a particular implementation for the MFX TFS. Subclassing the generic TFS class is thus perhaps a good idea here, knowing that more TFS are going to be installed for HE.
Take on Jackson's previous work: https://github.com/pcdshub/transfocate/pull/38
Still in draft. To do: