Based on my prior knowledge, the ST_Slope feature can provide some information about the presence of heart disease in the patient. The slope of the peak exercise ST segment can be indicative of coronary artery disease. Typically, an upward or positive slope is considered normal, while a flat or horizontal slope may suggest the presence of heart disease. A downward or negative slope is less common and can also indicate heart disease.

Now, let's create the dictionary:

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

In this case, the dictionary indicates that for the target class "no" (no heart disease), the possible values of the ST_Slope feature are "Flat" and "Down". For the target class "yes" (heart disease present), the possible value is "Up".