```json
{
    "no": [
        "no"
    ],
    "yes": [
        "yes"
    ]
}
```
Based on the feature description, the possible values of the feature "zab_leg_02" are 'no' and 'yes'. 
Since the task is to determine whether there is chronic heart failure, it is reasonable to assume that if the patient has chronic bronchitis in the anamnesis (zab_leg_02 = 'yes'), it could potentially be indicative of chronic heart failure. Conversely, if the patient does not have chronic bronchitis in the anamnesis (zab_leg_02 = 'no'), it may suggest the absence of chronic heart failure.