code: def test_slice(self):
      experiment = experiment_factory(
          id="e1",
          checkpoints=[
              checkpoint_factory(id="c1"),
              checkpoint_factory(id="c2"),
              checkpoint_factory(id="c3"),
          ],
      )
      assert isinstance(experiment.checkpoints[:2], CheckpointList)
  
file_path: keepsake/python/tests/test_checkpoint.py
imports: import datetime
  import time
  import os
  import pytest
  from waiting import wait
  from keepsake.checkpoint import Checkpoint, CheckpointList
  from keepsake.exceptions import DoesNotExist
  from keepsake.project import Project
  from tests.factories import experiment_factory, checkpoint_factory
label_desc: Use image node_id 3 for calling the TestCheckpointList obj's underlying member method code with example usage: obj.test_slice() without return types