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

Based on the given feature and task, the feature FIB_G_POST is a binary categorical variable that indicates whether the patient had Ventricular fibrillation at the time of admission to the intensive care unit. 

For the target class “no” (indicating absence of chronic heart failure), the possible value of FIB_G_POST is “no”. This suggests that patients who did not have Ventricular fibrillation at the time of admission to the intensive care unit do not have chronic heart failure.

For the target class “yes” (indicating presence of chronic heart failure), the possible value of FIB_G_POST is “yes”. This indicates that patients who had Ventricular fibrillation at the time of admission to the intensive care unit may have chronic heart failure.

Since FIB_G_POST is a binary categorical variable with only two possible values, there are no other values that need to be included in the dictionary.