sqlalchemy with existing DB schemma

#!/usr/bin/env python
import sqlalchemy
from sqlalchemy import create_engine,\
    Table, Column, Integer, String, MetaData, ForeignKey
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('sqlite:///places.sqlite')
Session = sessionmaker(bind=engine)
metadata = MetaData(engine)
Base = declarative_base()

moz_bookmarks = Table('moz_bookmarks', metadata,
#           Column('id', Integer(), primary_key=True, nullable=False),
            autoload=True)

class MozBookmarks(Base):
    __table__ = moz_bookmarks


for bookmark in Session().query(MozBookmarks)\
                .filter(MozBookmarks.id == 903):
    print bookmark, bookmark.title, bookmark.__dict__