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

Based on the given feature description, it appears that the feature "zab_leg_04" represents whether the patient has chronic pneumonia in their medical history. The target variable is whether the patient shows chronic heart failure.

From the description, it can be inferred that if a patient has chronic pneumonia in their medical history, it may contribute to the development of chronic heart failure. Therefore, the presence of chronic pneumonia may be an indicator that the patient shows chronic heart failure (target class "yes"). On the other hand, if the patient does not have chronic pneumonia in their medical history, it may suggest a lower likelihood of chronic heart failure (target class "no").

Based on this analysis, the possible values for the feature "zab_leg_04" in the target class "no" are ["no"], and the possible values in the target class "yes" are ["yes"].