Return a copy of the array for detector_key.train_id_coordinates()

[takluyver]

So that modifying the returned array doesn't affect the internals of the detector data objects.

This also means the .train_id_coordinates() method will consistently return a NumPy array - previously for JUNGFRAU it would have been a list. That's technically an API break, but I think the consistency is worth it.

cc @turkot - I spotted this while looking at the code to answer your question.

[philsmt]

I would say .train_id_coordinates() returning a list was a bug, given all other instances of this method in EXtra-data return ndarray (or pd.Series).

LGTM

[turkot]

Thank you Thomas, I agree that consistency has higher priority.

[takluyver]

Thanks both!