Based on prior knowledge, the feature "nr_03" represents the presence or absence of paroxysms of atrial fibrillation in the patient's medical history. To analyze the relationship between this feature and the presence of chronic heart failure, we need to examine the distribution of feature values for each target class.

Here is the dictionary representing the relationship between the feature "nr_03" and the task of predicting chronic heart failure:

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

Explanation:
- For the target class "no" (indicating absence of chronic heart failure), the feature value "no" is the only possible value.
- For the target class "yes" (indicating presence of chronic heart failure), the feature value "yes" is the only possible value.

Please note that the dictionary includes only the values that are relevant to the target classes. As there are no other possible values apart from "no" and "yes", the dictionaries for both target classes contain the respective value only.