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

Based on the given feature "n_p_ecg_p_12", we can see that there are only two categories, "no" and "yes". Therefore, for the target class "no" (chronic heart failure not present), the only possible value for the feature "n_p_ecg_p_12" is "no". Similarly, for the target class "yes" (chronic heart failure present), the only possible value for the feature "n_p_ecg_p_12" is "yes".