Serialize to JSON.

        :return string: serializaed JSON

def serialize(self, content):
        """ Serialize to JSON.

        :return string: serializaed JSON

        """
        worker = JSONSerializer(
            scheme=self.resource,
            options=self.resource._meta.emit_options,
            format=self.resource._meta.emit_format,
            **self.resource._meta.emit_models
        )
        return worker.serialize(content)