Sometimes you inherit a database full of junk. Maybe the previous developer put data in the database keys, which causes variety to go out of memory when run. After you've run the `logKeysContinuously` to figure out which subkeys may be a problem, you can use this option to run variety without those subkeys.
Analyzing a large collection on a busy replica set primary could take a lot longer than if you read from a secondary. To do so, we have to tell MongoDB it's okay to perform secondary reads
by setting the ```slaveOk``` property to ```true```: