code: def test_custom_motif_unknown():
      with pytest.raises(ValueError, match="motif structure of type"):
          CustomMotif(structure="unknown")
  
imports: import pytest
  import torch
  from torch_geometric.data import Data
  from torch_geometric.datasets.motif_generator import CustomMotif
  from torch_geometric.testing import withPackage
label_desc: Use image node_id 3 for calling a global function with example usage: test_custom_motif_unknown() without return types