code: def test_issue_1634(self):
      # tests: https://github.com/voxel51/fiftyone/issues/1634
      dataset = (
          foz.load_zoo_dataset("quickstart-video", max_samples=1)
          .select_fields("frames.detections")
          .clone()
      )
  
      anno_key = "issue_1634_test"
      results = dataset.annotate(
          anno_key,
          label_field="frames.ground_truth",
          label_type="detections",
          classes=["test"],
      )
  
      task_id = results.task_ids[0]
      with results:
          api = results.connect_to_api()
  
          # Create overlapping tracks of different type
          _create_annotation(
              api,
              task_id,
              track=(0, 30),
              _type="polygon",
              points=[10, 20, 40, 30, 50, 60],
          )
          _create_annotation(
              api,
              task_id,
              track=(20, 40),
          )
  
      imported_dataset = fo.Dataset()
      with etau.TempDir() as tmp:
          fouc.import_annotations(
              imported_dataset,
              task_ids=[task_id],
              data_path=tmp,
              download_media=True,
          )
          imported_dataset.compute_metadata()
          self.assertEqual(
              imported_dataset.first().metadata.total_frame_count,
              dataset.first().metadata.total_frame_count,
          )
          imported_dataset.export(
              export_dir=tmp, dataset_type=fo.types.CVATVideoDataset
          )
          filename = os.path.splitext(
              os.path.basename(imported_dataset.first().filepath)
          )[0]
          labels_filepath = os.path.join(
              tmp, "labels", "%s.xml" % filename
          )
          with open(labels_filepath, "r") as f:
              label_file_info = f.read()
              track_1 = '<track id="1" label="test">'
              track_2 = '<track id="2" label="test">'
              polygon_frame_0 = '<polygon frame="0"'
              polygon_frame_30 = '<polygon frame="30"'
              box_frame_20 = '<box frame="20"'
              box_frame_40 = '<box frame="40"'
              self.assertTrue(track_1 in label_file_info)
              self.assertTrue(track_2 in label_file_info)
              self.assertTrue(polygon_frame_0 in label_file_info)
              self.assertTrue(polygon_frame_30 in label_file_info)
              self.assertTrue(box_frame_20 in label_file_info)
              self.assertTrue(box_frame_40 in label_file_info)
  
          cvat_video_dataset = fo.Dataset.from_dir(
              dataset_dir=tmp,
              dataset_type=fo.types.CVATVideoDataset,
          )
          detections = cvat_video_dataset.values(
              "frames.detections", unwind=True
          )
          detections = [i for i in detections if i is not None]
          self.assertEqual(len(detections), 20)
          polylines = cvat_video_dataset.values(
              "frames.polylines", unwind=True
          )
          polylines = [i for i in polylines if i is not None]
          self.assertEqual(len(polylines), 30)
  
      dataset.load_annotations(anno_key, cleanup=True)
  
imports: from bson import ObjectId
  from collections import defaultdict
  import numpy
  import os
  import unittest
  import eta.core.utils
  import fiftyone
  import fiftyone.utils.cvat
  import fiftyone.zoo
  from fiftyone.core.expressions import ViewField
label_desc: Use image node_id 8 for calling the CVATTests obj's underlying member method code with example usage: obj.test_issue_1634() without return types