Based on prior knowledge, BMI can be a useful indicator for determining whether a person has diabetes. Generally, a higher BMI is associated with an increased risk of developing diabetes. However, it is important to note that BMI alone may not be sufficient for making a definitive diagnosis, as other factors such as age, genetics, and overall health should also be taken into consideration.

Here is the dictionary with the BMI values for each target class:

```json
{
	"yes": [25.0, 28.5, 30.2, 32.7, 35.1],
	"no": [18.5, 21.3, 23.8, 24.9, 26.4]
}
```

Please note that these values are just examples and may vary depending on the specific dataset and the cutoffs used to determine the target class.