code: def test_aggregate():
      vs = [Average(0.1), Average(0.3)]
      assert aggregate(vs) == 0.2
      vs = []
      assert aggregate(vs) is np.nan
      with pytest.raises(NotImplementedError):
          vs = [DummyReportedValue()]
          aggregate(vs)
  
imports: import logging
  import uuid
  from pathlib import Path
  import numpy
  import pytest
  import torch
  from torch.utils.tensorboard import SummaryWriter
  from espnet2.train.reporter import Average, ReportedValue, Reporter, aggregate
label_desc: Use image node_id 30 for calling a global function with example usage: test_aggregate() without return types