如何获得mongoose聚合函数的结果

mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => {
    console.log('Connected to MongoDB');
  })
  .catch((error) => {
    console.error('Error connecting to MongoDB', error);
  });

const pipeline = [
  { $match: { status: 'active' } },
  { $group: { _id: '$category', total: { $sum: '$quantity' } } },
  { $project: { category: '$_id', total: 1, _id: 0 } }
];

const Model = mongoose.model('Model', schema);
Model.aggregate(pipeline)
  .then((result) => {
    console.log(result);
  })
  .catch((error) => {
    console.error('Error executing aggregation', error);
  });