gistfile1.py

class Customers(Base):

    __tablename__ = 'customers'
    id = Column(Integer, primary_key=True)

    name = Column(Unicode)
    description = Column(Unicode)
    accounts = references('Accounts')

    comments = references('comments', backref='customers')

class Comments(Base):

    __tablename__ = 'comments'
    id = Column(Integer, primary_key=True)
    contents = Column(Unicode)
    customer_id = Column(Integer, ForeignKey('customers.id'))