def returns_json(func):
    """Decorator for functions which return JSON
    """
    def decorator(*args, **kwargs):
        instance = args[0]
        request = getattr(instance, 'request', None)
        request.response.setHeader("Content-Type", "application/json")
        result = func(*args, **kwargs)
        return json.dumps(result)
    return decorator
Decorator for functions which return JSON