This API is not set in stone, a higher-level one can be built on top of these functions. What you suggest @GaelVaroquaux is a good idea, it would reduce the number of functions and is easy to implement.

I do think, however, that keeping the "region_" prefix is useful, because some people will use _from region import *_ thus making call to 'to_list()'. This is not very explicit in my opinion.