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

Based on prior knowledge, we can analyze the relationship between the feature "nr_01" (Premature atrial contractions in the anamnesis) and the occurrence of chronic heart failure. 

For the class "no" (patients without chronic heart failure), the possible value for the feature "nr_01" is only "no". This indicates that patients without a history of premature atrial contractions in their medical history do not have chronic heart failure.

For the class "yes" (patients with chronic heart failure), the possible values for the feature "nr_01" can be "no" or "yes". This suggests that patients with a history of premature atrial contractions in their medical history may or may not have chronic heart failure.

It is important to note that this analysis is based on prior knowledge and further analysis of the data may be required to fully understand the relationship between the feature and the occurrence of chronic heart failure.