To analyze the relationship between the feature IBS_POST and the presence of chronic heart failure, we need to study the distribution of IBS_POST values for both the "yes" and "no" classes of the target variable.

Let's take a look at the data and examine the relationship:

| IBS_POST                                | Chronic Heart Failure |
|-----------------------------------------|-----------------------|
| there was no СHD                        | No                    |
| exertional angina pectoris               | Yes                   |
| unstable angina pectoris                 | No                    |
| there was no СHD                        | No                    |
| unstable angina pectoris                 | No                    |
| exertional angina pectoris               | Yes                   |
| there was no СHD                        | No                    |
| there was no СHD                        | No                    |
| unstable angina pectoris                 | No                    |
| there was no СHD                        | No                    |
| there was no СHD                        | No                    |
| exertional angina pectoris               | Yes                   |
| there was no СHD                        | No                    |
| there was no СHD                        | No                    |
| exertional angina pectoris               | Yes                   |
| unstable angina pectoris                 | No                    |
| unstable angina pectoris                 | No                    |
| there was no СHD                        | No                    |
| unstable angina pectoris                 | No                    |
| exertional angina pectoris               | Yes                   |

Based on this data, we can observe the following relationships:

- For the "no" class (patients without chronic heart failure), the possible values of IBS_POST are: 'there was no СHD' and 'unstable angina pectoris'.
- For the "yes" class (patients with chronic heart failure), the possible value of IBS_POST is 'exertional angina pectoris'.

Using this information, we can create the following dictionary:

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