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

Based on the given feature "ritm_ecg_p_02" (ECG rhythm at the time of admission to hospital – atrial fibrillation), there are two possible values: "no" and "yes". 

For patients who do not have chronic heart failure (target class "no"), the possible values of "ritm_ecg_p_02" are only "no".

For patients who have chronic heart failure (target class "yes"), the possible values of "ritm_ecg_p_02" are only "yes".

Therefore, the dictionary for the relationship between the feature and the task is as shown above.