[root@sgdb1 pg_comparator_wrapper]# python pg_comparator_wrapper.py
Traceback (most recent call last):
  File "pg_comparator_wrapper.py", line 119, in ?
    mapper(Transaction, transactions)
  File "/home/pgega/pg_comparator_wrapper/sqlalchemy/orm/__init__.py", line 670, in mapper
    return Mapper(class_, local_table, *args, **params)
  File "/home/pgega/pg_comparator_wrapper/sqlalchemy/orm/mapper.py", line 192, in __init__
    self._configure_pks()
  File "/home/pgega/pg_comparator_wrapper/sqlalchemy/orm/mapper.py", line 445, in _configure_pks
    raise sa_exc.ArgumentError("Mapper %s could not assemble any primary "
sqlalchemy.exc.ArgumentError: Mapper Mapper|Transaction|transactions could not assemble any primary key columns for mapped table 'transactions'