code: def test_empty_experiment_to_pb():
      project = Project()
      exp = empty_experiment(project)
      expected = empty_experiment_pb()
      assert pb_convert.experiment_to_pb(exp) == 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 16 for calling a global function with example usage: test_empty_experiment_to_pb() without return types