'Returns:
200 response with exists = True in json if bookmark exists.
404 with exists = False in json if no matching bookmark is found.
400 if json data is missing any one of: project, version, page.'

def post(self, request, *args, **kwargs):

    post_json = json.loads(request.body)
    try:
        project = post_json['project']
        version = post_json['version']
        page = post_json['page']
    except KeyError:
        return HttpResponseBadRequest(content=json.dumps({'error': 'Invalid    parameters'}))
    try:
        Bookmark.objects.get(project__slug=project, version__slug=version, page=page)
    except ObjectDoesNotExist:
        return HttpResponse(content=json.dumps({'exists': False}), status=404, content_type='application/json')
    return HttpResponse(content=json.dumps({'exists': True}), status=200, content_type='application/json')
