# redef fun to_s do return title
# redef fun ==(o) do return o isa SELF and id == o.id
# redef fun hash do return id.hash
-# redef fun to_json do return serialize_to_json
# end
#
# # We then need to subclass the `MongoRepository` to provide Book specific services.
redef fun hash do return id.hash
redef fun to_s do return id
- redef fun to_json do return serialize_to_json
end
# JsonObject can be used as a `RepositoryQuery`.