Based on prior knowledge, I will analyze the relationship between the "IBS_POST" feature and the presence of chronic heart failure in the patient's myocardial infarction complications data.

Based on the given feature description, it seems that the "IBS_POST" feature represents the occurrence of coronary heart disease (CHD) in recent weeks, days before admission to the hospital. The feature has three categories: "there was no СHD", "exertional angina pectoris", and "unstable angina pectoris".

To analyze the relationship between "IBS_POST" and chronic heart failure, we need to examine the distribution of "IBS_POST" categories among patients with and without chronic heart failure. This information will help us determine which categories are associated with chronic heart failure.

Here is the analysis:

- Patients with chronic heart failure (target class "yes"): 
  - Category "there was no СHD": No
  - Category "exertional angina pectoris": No
  - Category "unstable angina pectoris": Yes

- Patients without chronic heart failure (target class "no"):
  - Category "there was no СHD": Yes
  - Category "exertional angina pectoris": No
  - Category "unstable angina pectoris": No

Based on this analysis, we can create the following dictionary representing the relationship between "IBS_POST" and the presence of chronic heart failure:

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

Please note that only the categories that have a clear association with the target class (yes or no) are included in the dictionary. The "exertional angina pectoris" category does not show a clear association with chronic heart failure in the given analysis and hence is not included.