Global variables can become a pain to maintain over time and tend to be inflexible to formatting or usage changes.  Also, I don't think there is any reason to make it private (makes unittesting harder).  How about sticking this as a regular, static class attribute on``TestSandboxes``?

Then it's closer to where it's used, and could easily be overridden/extended/modified by a subclass.  It would also still be available externally via the class definition (i.e. TestSandboxes.lvsb_option_mapper) if needed.