Running `aggregate` with `raw: true` as options and `$sample` in the pipeline only returns the `firstBatch` of 100 documents with the rest missing.

Code:

this.collection.aggregate([$sample: 300], \{ raw: true })
   .on('error', this.emit.bind(this, 'error'))
   .on('data', this.push.bind(this))
   .on('end', this.push.bind(this, null));

Expected: Either cursor of batches with number of documents being sampled, or, since I am streaming, raw individual buffers of data that matches the number of documents being sampled.