code: def test_SubgraphSampler_invoke():
      itemset = gb.ItemSet(torch.arange(10), names="seed_nodes")
      item_sampler = gb.ItemSampler(itemset, batch_size=2).copy_to(
          F.ctx()
      )
  
      # Invoke via class constructor.
      datapipe = gb.SubgraphSampler(item_sampler)
      with pytest.raises(NotImplementedError):
          next(iter(datapipe))
  
      # Invokde via functional form.
      datapipe = item_sampler.sample_subgraph()
      with pytest.raises(NotImplementedError):
          next(iter(datapipe))
  
imports: import unittest
  from enum import Enum
  from functools import partial
  import backend
  import dgl
  import dgl.graphbolt
  import pytest
  import torch
  from torchdata.datapipes.iter import Mapper
  from .None import gb_test_utils
label_desc: Use image node_id 3 for calling a global function with example usage: test_SubgraphSampler_invoke() without return types