def normalize_ident(ident):
    '''Splits a generic identifier.

    If ``ident`` is a tuple, then ``(ident[0], ident[1])`` is returned.
    Otherwise, ``(ident[0], None)`` is returned.
    '''
    if isinstance(ident, tuple) and len(ident) == 2:
        return ident[0], ident[1]  # content_id, subtopic_id
    else:
        return ident, None
Splits a generic identifier.

    If ``ident`` is a tuple, then ``(ident[0], ident[1])`` is returned.
    Otherwise, ``(ident[0], None)`` is returned.