def split_obj_identifier(obj_identifier):
    """
    Break down the identifier representing the instance.

    Converts 'notes.note.23' into ('notes.note', 23).
    """
    bits = obj_identifier.split('.')

    if len(bits) < 2:
        return (None, None)

    pk = '.'.join(bits[2:])
    # In case Django ever handles full paths...
    object_path = '.'.join(bits[0:2])
    return (object_path, pk)