def get_thumbnail_preset(self):
        """
        Returns the format preset corresponding to this Node's type, or None if the node doesn't have a format preset.
        """
        if isinstance(self, ChannelNode):
            return format_presets.CHANNEL_THUMBNAIL
        elif isinstance(self, TopicNode):
            return format_presets.TOPIC_THUMBNAIL
        elif isinstance(self, VideoNode):
            return format_presets.VIDEO_THUMBNAIL
        elif isinstance(self, AudioNode):
            return format_presets.AUDIO_THUMBNAIL
        elif isinstance(self, DocumentNode):
            return format_presets.DOCUMENT_THUMBNAIL
        elif isinstance(self, ExerciseNode):
            return format_presets.EXERCISE_THUMBNAIL
        elif isinstance(self, HTML5AppNode):
            return format_presets.HTML5_THUMBNAIL
        else:
            return None
Returns the format preset corresponding to this Node's type, or None if the node doesn't have a format preset.