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

Based on prior knowledge, the n_p_ecg_p_12 feature indicates the presence or absence of Complete Right Bundle Branch Block (RBBB) on the Electrocardiogram (ECG) at the time of admission to the hospital. 

In the context of myocardial infarction complications data, a complete RBBB pattern on ECG may suggest the presence of chronic heart failure. Therefore, if the value of n_p_ecg_p_12 is "yes", it is likely that the patient shows chronic heart failure. On the other hand, if the value is "no", it indicates the absence of complete RBBB and suggests no chronic heart failure.

Therefore, the possible values of feature n_p_ecg_p_12 for the target class "no" are ["no"], and for the target class "yes" are ["yes"].