It looks like it's there in pymarc as well:

https://github.com/edsu/pymarc/blob/master/pymarc/record.py#L386


On 09/03/2013 03:02 PM, Bill Dueber wrote:
> I can see where you might think that "no progress has been made" because
> the only real document of the format is that old, old blog post.
>
> The problem, however, is not a lack of progress but a lack of documentation
> of that progress. File_MARC (PHP), MARC::Record (perl), ruby-marc (ruby)
> and marc4j (java) will all deal, to one extent or another, either with the
> JSON directly or with a hash/map data structure that maps directly to that
> JSON structure.
>
> [BTW, can anyone summarize the state of pymarc wrt marc-in-json?]
>
>
>
>
>
> On Tue, Sep 3, 2013 at 5:09 AM, dasos ili <[log in to unmask]> wrote:
>
>> It is exactly three years back, and no real progress has been made
>> concerning  this proposal to serialize MARC in JSON:
>>
>>
>> http://dilettantes.code4lib.org/blog/2010/09/a-proposal-to-serialize-marc-in-json/
>>
>>
>> Meanwhile new tools for searching and retrieving records have come in,
>> such as Solr and Elasticsearch. Any ideas on how one could alter (or
>> propose a new format) more suited to the mechanisms of these two search
>> platforms?
>>
>> Any example implemantations would be also really appreciated,
>>
>> thank you in advance
>>
>
>