ModelRelationsDefinition: NonEnumerableRecordCodec<TrivialCodec<string>, UnionCodec<[ExactCodec<TypeCodec<{ type: LiteralCodec<"account"> }>>, ExactCodec<TypeCodec<{ model: RefinementCodec<TrivialCodec<string>, string>; type: LiteralCodec<"document"> }>>]>> = ...

A mapping between model's property names and types of relation properties

It indicates which properties of a model are relation properties and of what type