Two calls to createIndex when using with two collections?

[dandv]

Thanks for the solution to #83! I'm using that to add autoincrementing fields to two collections:

@plugin(AutoIncrement, { inc_field: 'fooId', start_seq: 200 })
export class Foo extends defaultClasses.TimeStamps {
  ...
}

// In another file
@plugin(AutoIncrement, { inc_field: 'barId', start_seq: 500 })
export class Bar extends defaultClasses.TimeStamps {
  ...
}

I've enabled mongoose debugging and saw two calls to counters.createIndex:

Mongoose: counters.createIndex({ id: 1, reference_value: 1 }, { unique: true, background: true })
Mongoose: counters.createIndex({ id: 1, reference_value: 1 }, { unique: true, background: true })

Just wanted to check if this is expected. Would one call be enough? Thanks!