async def METHOD_NAME(self, event):
    """
    Handler for calls like::
        channel_layer.group_send(group_name, {
            'type': 'notify',  # This routes it to this handler.
            'group': group_name,
            'content': json_message,
        })
    """
    # Take lock out of redis for this message:
    await clear_message_semaphore(self.channel_layer, event)
    if "content" in event:
        await self.send_json(event["content"])
        return
    if "serializer" in event and "instance" in event and "inner_type" in event:
        message = await self.serialize_instance_as_message(event)
        await self.send_json(message)
        return