At this point, the learner hasn't seen functions, the Enum module, or
the pipe operator, so it feels like a little much to add that here. The
reason it's needed is that the order of keys/1 and values/1 is reverse
of how it's defined. This is due to an implementation detail in Erlang's
maps. We /could/ use this as a learning opportunity rather than sorting
them, but I'm not sure what could be said about that...
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