See Sourcery.

The models first require a list of properties with various types and some are optional. The init function must then know the keys and structure of the JSON file in order to process it properly and also handle the non-optional and optional properties. It may not be an easy task to generate this code but if it is possible it would greatly simplify development for an API client.

A model like Map shows how the properties and init function handle non-optional and optional values when parsing the JSON.