You'll see that this dataset already comes with a training set containing 1000 images and a test set with 29 images.
To get familiar with the data, explore what the examples look like.

cppe5["train"][0]
{'image_id': 15,
 'image': ,
 'width': 943,
 'height': 663,
 'objects': {'id': [114, 115, 116, 117],
  'area': [3796, 1596, 152768, 81002],
  'bbox': [[302.0, 109.0, 73.0, 52.0],
   [810.0, 100.0, 57.0, 28.0],
   [160.0, 31.0, 248.0, 616.0],
   [741.0, 68.0, 202.0, 401.0]],
  'category': [4, 4, 0, 0]}}