How to include a subquery in a SELECT clause?

Question

I'm trying to convert the following SQL:

select t1.id_
     , t1.field_a
     , (select t2.field_c 
        from belgarath.test_2 t2 
       where t2.field_a = t1.field_a 
         and t2.field_b = 1) test_2_field_b_1
     , (select t2.field_c 
        from belgarath.test_2 t2 
       where t2.field_a = t1.field_a 
         and t2.field_b = 2) test_2_field_b_2
     from belgarath.test_1 t1

I've got as far as this:

sq1 = session.query(Test2.field_C)
sq1 = sq1.filter(Test2.field_A.__eq__(Test1.field_A), Test2.field_B.__eq__(1))
sq1 = sq1.subquery(name="test_2_field_b_1")

sq2 = session.query(Test2.field_C)
sq2 = sq2.filter(Test2.field_A.__eq__(Test1.field_A), Test2.field_B.__eq__(2))
sq2 = sq2.subquery(name="test_2_field_b_2")

session.query(Test1.id_, Test2.field_A, sq1, sq2)

But I'm getting the following SQL:

SELECT belgarath.test_1.id_ AS belgarath_test_1_id_, belgarath.test_2.`field_A` AS `belgarath_test_2_field_A`, test_2_field_b_1.`field_C` AS `test_2_field_b_1_field_C`, test_2_field_b_2.`field_C` AS `test_2_field_b_2_field_C` 
FROM belgarath.test_1, belgarath.test_2, (SELECT belgarath.test_2.`field_C` AS `field_C`
FROM belgarath.test_2, belgarath.test_1
WHERE belgarath.test_2.`field_A` = belgarath.test_1.`field_A` AND belgarath.test_2.`field_B` = %(field_B_1)s) AS test_2_field_b_1, (SELECT belgarath.test_2.`field_C` AS `field_C`
FROM belgarath.test_2, belgarath.test_1
WHERE belgarath.test_2.`field_A` = belgarath.test_1.`field_A` AND belgarath.test_2.`field_B` = %(field_B_2)s) AS test_2_field_b_2

It looks like SQLAlchemy is pushing the sub queries into the FROM clause...

Here are the table classes if it helps:

class Test1(Base):
    __tablename__ = "test_1"

    field_A = Column(Integer)


class Test2(Base):
    __tablename__ = "test_2"

    field_A = Column(Integer)
    field_B = Column(Integer)
    field_C = Column(String(3))