unable to access fields of relationship via render_table

Hi,

I am unable to access product.name in my html. When using the "for item loop" I am able to print item.product.name. However in titles when using product.name it will remain empty. Typing only 'product' will correctly display .

What am I doing wrong?

app.py
```
@app.route('/cost_calculation//view')
def view_cost_calculation(cost_calculation_id):
# Details of Calculation
cost_calculation = CostCalculation.query.get(cost_calculation_id)

cost_calculation_items = CostCalculationItem.query.filter_by(cost_calculation_id=cost_calculation_id).all()
from pprint import pprint
pprint(cost_calculation_items)
for item in cost_calculation_items:
pprint(item)
print(f"{item.product.name}: {item.unit_price}")
print(f"{item.product.product_detail}: {item.unit_price}")

titles = [('id', '#'),('product', 'Product Name'),('name', 'Product Name'),('product.name', 'Product Name'), ('quantity', 'Quantity'), ('unit_price', 'Price')]

return render_template('cost_calculation_view.html',
cost_calculation=cost_calculation,
cost_calculation_items=cost_calculation_items,
CostCalculationItem=CostCalculationItem,
titles=titles)
```

Log:
```
[, ]

Virtual Server (EC2): 10
Dummy product description for Virtual Server (EC2): 10

Database (RDS): 5
```

html:
```
{{ render_table(cost_calculation_items, titles=titles, primary_key='id', urlize_columns=(''), show_actions=True, model=CostCalculationItem,
view_url=('view_cost_calculation_item', [('cost_calculation_item_id', ':id')]),
edit_url=('edit_cost_calculation_item', [('cost_calculation_item_id', ':id')]),
delete_url=('delete_cost_calculation_item', [('cost_calculation_item_id', ':id')]),
new_url=url_for('list_products'))}}
```

model:
```
class Product(db.Model):
__tablename__ = 'product'

id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(), nullable=False)
product_price = db.Column(db.DECIMAL, nullable=False)
product_detail = db.Column(db.String())
# cost_calculation_item = db.relationship('CostCalculationItem')

class CostCalculationItem(db.Model):
__tablename__ = 'cost_calculation_item'

id = db.Column(db.Integer, primary_key=True)
description = db.Column(db.String(), nullable=True)
quantity = db.Column(db.Integer, nullable=False)
unit_price = db.Column(db.DECIMAL, nullable=False)
cost_calculation_id = db.Column(db.Integer, db.ForeignKey('cost_calculation.id'), nullable=False)
cost_calculation = db.relationship('CostCalculation', backref='cost_calculation_items')

product_id = db.Column(db.Integer, db.ForeignKey('product.id'), nullable=False)
product = db.relationship('Product', backref='cost_calculation_items')
```