Based on prior knowledge, we can analyze the relationship between the feature "nr_03" and the task of determining if the patient shows chronic heart failure.

Based on the feature description, "nr_03" represents the presence or absence of Paroxysms of atrial fibrillation in the patient's medical history. Atrial fibrillation is a type of irregular heart rhythm that can be a risk factor for chronic heart failure.

To determine the relationship between "nr_03" and chronic heart failure, we can hypothesize the following:

1. If the patient has a history of Paroxysms of atrial fibrillation (nr_03 = "yes"), it is more likely that they may show signs of chronic heart failure.
2. If the patient does not have a history of Paroxysms of atrial fibrillation (nr_03 = "no"), it is less likely that they may show signs of chronic heart failure.

Based on this analysis, we can create a dictionary as follows:

```json
{
	"no": ["no"],
	"yes": ["yes"]
}
```

In this case, both target classes have only one possible value for the feature "nr_03".