code: def test_checkpoint_to_pb():
      chk = full_checkpoint()
      expected = full_checkpoint_pb()
      assert pb_convert.checkpoint_to_pb(chk) == expected
  
imports: import datetime
  from keepsake import pb_convert
  from keepsake.checkpoint import Checkpoint, PrimaryMetric, CheckpointList
  from keepsake.experiment import Experiment
  from keepsake.servicepb import keepsake_pb2
  from keepsake.project import Project
label_desc: Use image node_id 13 for calling a global function with example usage: test_checkpoint_to_pb() without return types