```json
{
	"no": ["no"],
	"yes": ["yes"]
}
```
Since the feature "n_r_ecg_p_03" is a categorical variable with categories "no" and "yes", we can see that there is a direct mapping between the feature and the target class. In the case of chronic heart failure, the absence of ventricular contractions on ECG at the time of admission to the hospital ("n_r_ecg_p_03" = "no") indicates that the patient does not have chronic heart failure, while the presence of ventricular contractions ("n_r_ecg_p_03" = "yes") indicates that the patient does have chronic heart failure. Therefore, the possible values of the "n_r_ecg_p_03" feature for the target class "no" are ["no"] and for the target class "yes" are ["yes"].