db.getCollection('trucks').aggregate([
   {
    $lookup: {
      from: 'loads',
      as: 'seats',
      localField: '_id',
      foreignField: 'truckId',
    },
  },
  {
    $project: {
      driver: 0,
       __v: 0,
    },
    {
      $graphLookup: {
         from: < here I just want to use the previous stage's output >,
         startWith: "$driverId",
         connectFromField: "driverId",
         connectToField: "_id",
         as: "driver"
      }
    }
])