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

Based on the feature description and task, it appears that the FIB_G_POST feature is related to the presence or absence of ventricular fibrillation at the time of admission to the intensive care unit (ICU). 

Looking at the categories of the FIB_G_POST feature, it consists of two possibilities: "no" and "yes". Therefore, the possible values of the FIB_G_POST feature for the target class "no" would be ["no"], indicating that there is no ventricular fibrillation at the time of admission to the ICU. 

Similarly, the possible values of the FIB_G_POST feature for the target class "yes" would be ["yes"], indicating that there is ventricular fibrillation at the time of admission to the ICU. 

It is important to note that this analysis is based on the given feature description and task, and does not take into account any additional factors or dependencies that may exist in the data.