我在mysql中有一个查询：

SELECT
    O.id,
    O.label,
    A.name
FROM
    organizations O
JOIN activities_area A JOIN assoc_organization_activities S ON
    O.identifier = S.organization_id AND A.identifier = S.activities_area_id
ORDER BY
    O.label

我正在尝试用sqlalchemy：

A = aliased(model.Activities, name='A')
S = aliased(model.AssocOrganizationsActivities, name='S')
O = aliased(model.Organizations, name='O')

organizations_query = session.query(O.id, O.label, A.name) \
                             .join(A) \
                             .join(S) \
                             .filter(O.identifier == S.organization_id) \
                             .filter(A.identifier == S.activities_area_id) \
                             .order_by(O.label) \
                             .all()

但这给了我一个错误：

InvalidRequestError: Could not find a FROM clause to join from. Tried joining to <class 'model.model.Activities'>, but got: Can't find any foreign key relationships between 'organizations' and 'activities_area'.

assocorganizationsactivities表只有3个字段：id、作为外键的组织id和作为外键的活动区域id。因此，表组织和活动都由关联组织活动链接。
如何让它工作？