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

Based on the given feature description and task, there are only two possible values for the feature FIB_G_POST: "no" and "yes". Therefore, the relationship between the feature and target can be analyzed as follows:

- For the target class "no" (indicating no chronic heart failure), the possible value of the feature FIB_G_POST is only "no".
- For the target class "yes" (indicating chronic heart failure), the possible value of the feature FIB_G_POST is only "yes".

Note that there are no other possible values mentioned, so the lists for each target class are not empty.