Prisma

Using prisma binding, the following query is failing and is just returning all vehicles. I'm having a hard time finding docs on querying for the presence or absence of relations in prisma binding... anybody know what I'm doing wrong here?

```
const vehicles =  await this.db.query.vehicles({
        filter: {
          driver_not: null,
        },
      }, '{vehicleID, driver {driverID}}')
```

Simple fix. This seemed to do it:

```
 const vehicles =  await this.db.query.vehicles({
        where: {
          driver: {
            driverID_not: null,
          },
        },
      }, '{vehicleID, driver {driverID}}')
```