sqlalchemy.exc.ProgrammingError Flask SQLAlchemy cannot read data from my table

class data_reader(db.Model):
    sno = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(30))

class data_reader(db.Model):
    __tablename__ = 'kolkata'
    sno = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(30))