docs: def _converter(data):
      """Internal function that will be passed to the native `json.dumps`.
  
      This function uses the `REGISTRY` of serializers and try to convert
      a given instance to an object that json.dumps can understand.
      """
      handler = REGISTRY.get(data.__class__)
      if handler:
          full_name = '{}.{}'.format(
              data.__class__.__module__,
              data.__class__.__name__)
          return {
              '__class__': full_name,
              '__value__': handler(data),
          }
      raise TypeError(repr(data) + " is not JSON serializable")