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

Based on my prior knowledge, the feature "ST_Slope" has a significant relation to the presence of heart disease. The ST segment represents the electrical activity of the heart, and changes in its slope can indicate abnormalities. In patients without heart disease (target class "no"), the ST segment slope is more likely to be "Up" or "Flat". On the other hand, in patients with heart disease (target class "yes"), the ST segment slope is more likely to be "Down". Other values of ST_Slope are not included in the dictionary since they are less predictable or have less relevance to the task.