Documentation error: model.add_labels() example uses string instead of Formula

[tronmon]

In the Python API documentation, the example for model.add_labels() uses:

model.add_labels({
'Smokes': {
'Ivan': Fact.TRUE,
'Nick': Fact.TRUE}
})

However, running this code raises:
AttributeError: 'str' object has no attribute 'formula_number'

It appears that model.add_labels() expects a Formula object (e.g., Smokes), not a string.

Replacing:
'Smokes'

With
Smokes

resolves the issue.