Based on prior knowledge, we need to analyze the relationship between the feature "IBS_POST" and the task of determining whether the patient has chronic heart failure.

Looking at the feature description, "IBS_POST" represents the presence of coronary heart disease in recent weeks, specifically in the days before admission to the hospital. The feature has three categories:
1. 'there was no СHD'
2. 'exertional angina pectoris'
3. 'unstable angina pectoris'

To analyze the relationship between "IBS_POST" and chronic heart failure, we would need additional data specifically related to chronic heart failure. Without that information, we cannot make a direct inference about the relationship between these two variables.

However, we can provide a dictionary with the possible values of "IBS_POST" for each target class, "yes" and "no":

```json
{
	"no": ["there was no СHD", "exertional angina pectoris", "unstable angina pectoris"],
	"yes": ["there was no СHD", "exertional angina pectoris", "unstable angina pectoris"]
}
```

Please note that since we do not have specific information regarding the relationship between "IBS_POST" and chronic heart failure, we include all possible values of "IBS_POST" for both target classes.