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

Based on the given feature description and task, it seems that the presence of premature atrial contractions in the anamnesis (nr_01) is being used to determine the presence of chronic heart failure. 

The feature nr_01 is a categorical variable with two categories: 'no' and 'yes'. In this case, the values 'no' and 'yes' directly correspond to the absence or presence of premature atrial contractions in the anamnesis, respectively. 

Since the feature nr_01 is being used to determine the presence of chronic heart failure, we can create a dictionary with the possible values of nr_01 for each target class. In this case, the dictionary would be:

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

This indicates that for the target class "no" (indicating absence of chronic heart failure), the only possible value of nr_01 is "no". Similarly, for the target class "yes" (indicating presence of chronic heart failure), the only possible value of nr_01 is "yes".