Redshift Datashare and Python Flask backend with SQALAlchemy

Question

I am using AWS Redshift Datashare. I can query my main redshift database from the datashare database like

select * from maindb.public.old_table limit 10;

in my IDE terminal.

However in my Python backend code, we are using the ORM structure, where we have models like

class oldTable(Model):
    __tablename__ = "maindb.public.old_table”
    __table_args__ = {"extend_existing": True}
    views = Column(db.Text, default=dt.datetime.utcnow, primary_key=True)

In my python FLASK backend code. Setting the table name to “maindb.public.old_table” doesn’t work to query the table. I get an error

(psycopg2.errors.UndefinedTable) relation \"maindb.public.old_table\" does not exist\n\n

Could someone help me to query it in my Python backend?

I know the approach using raw SQL text works but I prefer to keep it as models, and I don’t want to restructure everything