Based on my analysis, there is a relationship between the lug_boot feature and the decision to buy the car. Here is the dictionary describing the relationship:

```json
{
    "unacceptable": ["small"],
    "acceptable": ["med"],
    "good": ["med"],
    "very good": ["big"]
}
```

In this case, only the value 'med' of the feature lug_boot is associated with more than one target class. The value 'small' is associated with the target class 'unacceptable', the value 'med' is associated with the target classes 'acceptable' and 'good', and the value 'big' is associated with the target class 'very good'.