Parse json if json else leave as is

I wanted the filter to parse a message as json if it is json, otherwise just let it be in the form it is. There wasn't a lot of documentation on the filter description page so I was not sure if this is the default behavior already. If not, what is the best way to achieve this result?

I suggest installing v3.0.2+ of the plugin and setting skip_on_invalid_json => true.