Thanks nlust. I see your point. I've attempted to address it by adding a static member function to ApertureFluxAlgorithm which generates field names and is exposed to Python. This means that formatting is defined in exactly one place. I'm not sure that I'd want to go further in terms of exposing this to configuration etc, as it seems like that would be adding a lot of complexity to what should be a simple operation – I'd rather cross that bridge when we come to it.
I'm only semi-happy with the approach adopted, as I don't really like burdening the ApertureFluxAlgorithm interface in this way. Would you mind taking a look to see what you think and if you have any better ideas? Commit is here; I'll squash it into the rest of the PR if & when we decide if this is the approach we actually want to take.