Could I access other Collections in `mapReduce ` in mongo

help
1

I have 2 collections: CollectionA, CollectionB.
Could I access other collection in mapReduce
Eg.

CollectionA.rawCollection().mapReduce(
  function ()..........,
  function () {
    let getB = CollectionB.findOne() // Access other collections
    .........
  },
  {
    scope: { CollectionB: CollectionB }
  }
)

Please help me