def get_unnasigned_json(json_data,populated_object):
    """
       Given an object which has had fields assigned to it, as well as the 
       JSON dict from which these values were retrieved, this function returns
       a list of keys that were not used for populating the object.
       
       In order to match the attribute names and dictionary keys must have the
       same names.
    """
    if len(json_data) == 0:
        return {}
    else:
        temp_keys = populated_object.__dict__.keys()
        return dict((key,json_data[key]) for key in set(json_data) if key not in temp_keys)