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

Based on the given feature description and task, there seems to be an inverse relationship between the use of anticoagulants in the ICU (GEPAR_S_n) and the presence of chronic heart failure. In other words, if the patient has chronic heart failure, the value for GEPAR_S_n is most likely "no", and vice versa.

Since the feature is a categorical variable with only two possible values ("yes" and "no"), the possible values of GEPAR_S_n for the target class "no" would be ["yes"], indicating that patients without chronic heart failure tend to have used anticoagulants in the ICU. On the other hand, the possible values of GEPAR_S_n for the target class "yes" would be ["no"], indicating that patients with chronic heart failure tend to not have used anticoagulants in the ICU.

Please note that since the feature description and analysis are based on prior knowledge and assumptions, the actual relationship between the feature and the task should be further validated with data and domain expertise.