error in declarative adjacency lit relationship (in 0.5.0rc4)

I have a CMS page model which looks like this:

class Page(BaseObject):
    """A page in the CMS."""

    __tablename__ = "page"
    id = schema.Column(types.Integer(), primary_key=True, autoincrement=True)
    path = schema.Column(types.Unicode(128), nullable=False, index=True)
    parent_id = schema.Column(types.Integer(), 
        schema.ForeignKey("page.id", onupdate="CASCADE", ondelete="CASCADE"),
        nullable=False, index=True)
    children = orm.relation("Page", cascade="all",
            backref=orm.backref("parent", remote_side=["page.id"]("page.id")),
            collection_class=attribute_mapped_collection("path"))

this apears to work fine and the table is correct created in the database. However on the first query I do in that database for a completely unrelated object I get this:

  File "/Users/wichert/Development/2style4you/code/buildout/devel/src/2style4you/2style4you/websetup.py", line 21, in setup_app
    existing_accounts=[for account in meta.Session.query(Editor)](account.login)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/scoping.py", line 121, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/session.py", line 908, in query
    return self._query_cls(entities, self, **kwargs)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/query.py", line 95, in __init__
    self.__setup_aliasizers(self._entities)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/query.py", line 109, in __setup_aliasizers
    mapper, selectable, is_aliased_class = _entity_info(entity)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/util.py", line 466, in _entity_info
    mapper = class_mapper(entity, compile)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/util.py", line 543, in class_mapper
    mapper = mapper.compile()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/mapper.py", line 679, in compile
    mapper._post_configure_properties()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/mapper.py", line 701, in _post_configure_properties
    prop.init(key, self)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/interfaces.py", line 404, in init
    self.do_init()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/properties.py", line 579, in do_init
    self._post_init()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/properties.py", line 838, in _post_init
    self.backref.compile(self)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/properties.py", line 989, in compile
    mapper._compile_property(self.key, relation);
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/mapper.py", line 643, in _compile_property
    prop.init(key, self)
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/interfaces.py", line 404, in init
    self.do_init()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/properties.py", line 578, in do_init
    self._determine_local_remote_pairs()
  File "/Users/wichert/Library/eggs/SQLAlchemy-0.5.0rc4-py2.4.egg/sqlalchemy/orm/properties.py", line 814, in _determine_local_remote_pairs
    self.local_side, self.remote_side = [for x in zip(*list(self.local_remote_pairs))](util.OrderedSet(x))
ValueError: need more than 0 values to unpack

I put a pdb.set_trace() in there to see what self looked like:

(Pdb) p self
<sqlalchemy.orm.properties.PropertyLoader object at 0x26ed950>
(Pdb) pp self.__dict__
{'_PropertyLoader__join_cache': {},
 '_compiled': True,
 '_creation_order': 498,
 '_foreign_keys': set([Integer(), ForeignKey('page.id'), table=<page>, nullable=False)](Column('parent_id',)),
 '_is_backref': True,
 '_reverse_property': None,
 'argument': <Mapper at 0x24c5970; Page>,
 'backref': <sqlalchemy.orm.properties.BackRef object at 0x26ed910>,
 'cascade': CascadeOptions('save_update,merge'),
 'collection_class': None,
 'comparator': <sqlalchemy.orm.properties.Comparator object at 0x26ed970>,
 'comparator_factory': <class 'sqlalchemy.orm.properties.Comparator'>,
 'direction': <symbol 'MANYTOONE>,
 'enable_typechecks': True,
 'extension': None,
 'join_depth': None,
 'key': 'parent',
 'lazy': True,
 'local_remote_pairs': ['mapper': <Mapper at 0x24c5970; Page>,
 'order_by': False,
 'parent': <Mapper at 0x24c5970; Page>,
 'passive_deletes': False,
 'passive_updates': True,
 'post_update': False,
 'primaryjoin': <sqlalchemy.sql.expression._BinaryExpression object at 0x26eda10>,
 'remote_side': set([<sqlalchemy.sql.expression._ColumnClause at 0x26eda30; page.id>](],
)),
 'secondary': None,
 'secondary_synchronize_pairs': None,
 'secondaryjoin': None,
 'strategy_class': <class 'sqlalchemy.orm.strategies.LazyLoader'>,
 'synchronize_pairs': [Integer(), table=<page>, primary_key=True, nullable=False),
                        Column('parent_id', Integer(), ForeignKey('page.id'), table=<page>, nullable=False))]((Column('id',),
 'table': Table('page', MetaData(Engine(postgres://2style4you@/2style4you)), Column('id', Integer(), table=<page>, primary_key=True, nullable=False), Column('path', Unicode(length=128), table=<page>, nullable=False), Column('parent_id', Integer(), ForeignKey('page.id'), table=<page>, nullable=False), schema=None),
 'target': Table('page', MetaData(Engine(postgres://2style4you@/2style4you)), Column('id', Integer(), table=<page>, primary_key=True, nullable=False), Column('path', Unicode(length=128), table=<page>, nullable=False), Column('parent_id', Integer(), ForeignKey('page.id'), table=<page>, nullable=False), schema=None),
 'uselist': None,
 'viewonly': False}

the problem appears to be in the backref of the children relation: as soon as I remove that things work fine.

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