```json
{
    "no": ["no"],
    "yes": ["yes"]
}
```
Since the feature "n_r_ecg_p_04" is a categorical variable with two categories, "yes" and "no", and the task is to determine if the patient has chronic heart failure, we can assume that the presence of frequent premature ventricular contractions on ECG at the time of admission to the hospital ("yes" category) may indicate the possibility of chronic heart failure. On the other hand, the absence of frequent premature ventricular contractions ("no" category) might suggest no chronic heart failure. Therefore, the relationship between the feature and the target indicates that if the patient has "yes" as the value for the feature, it is likely to show chronic heart failure, while if the value is "no", it is less likely to show chronic heart failure.