Based on prior knowledge, the slope of the peak exercise ST segment (ST_Slope) can provide information about the presence of heart disease. Here's an analysis of the relationship between the feature and the task:

- Up Slope: In general, an upward slope of the ST segment during exercise may indicate the absence of heart disease or a less severe condition. Therefore, it is more likely to be associated with the target class "no".

- Flat Slope: A flat slope of the ST segment during exercise is often considered inconclusive and less informative for determining the presence of heart disease. Therefore, it is hard to predict its relationship with the target class, and we may exclude it from the final dictionary.

- Down Slope: A downward slope of the ST segment during exercise is more commonly associated with the presence of heart disease or a more severe condition. Thus, it is more likely to be associated with the target class "yes".

Based on this analysis, the dictionary can be created as follows:

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

Please note that the "Flat" slope value is excluded from the dictionary as it is inconclusive for determining the presence of heart disease.