Join table into itself after a union in sqlalchemy

I have two tables

Table one: org with 3 columns (org_code,chart_code, org_name)
Table two: org_2 with 2 columns (org_code,chart_code)

The represent different sources of data.

I need to do a union on the two but also to get the org_name from the first table.

Since the two don't line-up I figured I should do a union of query on table one and query on table two based on the shared columns and then try to join the query onto the first table

query1 = db.query(org.chart_coded ,org.org_code).filter(some filters)

query2 = db.query(org2.chart_code ,org2.org_code).filter(some filters)
union_query = query.union(query2)

this part of the union works well, but when I am trying to do the join I can't figure out how to specify the join condition of joining org.org_code onto the query.

join_query = union_query.join()

I don't know the SQLAlchemy syntax, but the plain SQL is:

SELECT org.org_code, org.chart_code, org.org_name
FROM org

UNION

SELECT org2.org_code, org2.chart_code, org1.org_name
FROM org
JOIN org2 ON org.org_code = org2.org_code

This