Q. Pluck fields not serializing in nested relationship

[noeunkim]

I got an issue where Pluck fields are not serializing correctly in a nested relationship.
This is an example related with my question:

I found screw_size and screw_total are serializing correctly, but test_screw_size and test_screw_total (which use Pluck) are not being included in the serialized output.
Is there a way to make Pluck work in this scenario without modifying the query?

# Model and Schema
Class Robot(Base):
    __tablename__ = "robot"
    __table_args__ = {"schema": "test"}
    id = Column(Integer, primary_key=True)
    age = Column(Integer)
    size = Column(Integer)
    total = Column(Integer)
    ...
    nail = relationship("Nail", primaryjoin="Robot.part == foreign(Nail.part)")

Class Nail(Base):
    __tablename__ = "nail"
    __table_args__ = {"schema": "test"}
    size = Column(Integer, primary_key=True)
    total = Column(Integer)
    ...
    screw = relationship("Screw", primaryjoin="Nail.id == foreign(Screw.id)")

Class Screw(Base):
    __tablename__ = "screw"
    __table_args__ = {"schema": "test"}
    size = Column(Integer, primary_key=True)
    total = Column(Integer)
    ...

class NailSchema(BaseSchema):
    """Schema for Nail Model"""

    _model = Nail
    screw_size = fields.Str(attribute="screw.size")
    screw_total = fields.Str(attribute="screw.total")
    
    # TODO: need to solve, why this is not working?
    test_screw_size = fields.Pluck(ScrewSchema, "size")
    test_screw_total = fields.Pluck(ScrewSchema, "total")

class ScrewSchema(BaseSchema):
    """Schema for Screw Model"""

    _model = Screw

class RobotSchema(BaseSchema):
    """Schema for Robot Model"""

    _model = Robot
    nail_part = fields.Method("get_nail")

    @staticmethod
    def get_nail(obj: Robot) -> dict | None:
        return NailSchema(many=True).dump(obj.nail)

# Query
robots = session.query(Nail).options(joinedload(Nail.screw))
nails = (
    session.query(Robot.id, Robot.age)
    .options(joinedload(Nail.screw)
)
nail_alias = aliased(Nail, nails)
robot_alias = aliased(Roboy, robots)

robots_with_nail = (
    session.query(robot_alias)
    .outerjoin(nail_alias, nail_alias.size == robot_alias.size)
    .options(contains_eager(robot_alias.nail))
)
test_result = RobotSchema(many=True).dump(robots_with_nail)