Based on prior knowledge, it is difficult to determine the relationship between the feature "nr_04" and the presence of chronic heart failure without additional information or a specific dataset. 

However, for the given task, we can assume that the feature "nr_04" represents a persistent form of atrial fibrillation in the patient's medical history. In this case, if the patient has a persistent form of atrial fibrillation ("yes" category), it is more likely that they may show chronic heart failure.

Based on this assumption, we can create a dictionary with the possible values of the feature "nr_04" for each target class:

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

Please note that this dictionary assumes that there are no other possible values for "nr_04" apart from "no" and "yes". If there are additional possible values, please provide the complete list, and I can update the dictionary accordingly.