At the moment when we use an attribute/convention it is propagated to a single child serializer, but there are cases in which multiple children serializers could be involved. This can happen, for instance, with a dictionary, where there are two children serializers.
At the moment we do not have a way of specifying different kind of behaviour/representation for the serializers of all the children serializers. For instance, using `BsonRepresentationAttribute` on a dictionary will have effect only on the serializers for the values, and not for the keys. We need to investigate how to solve this.