code: def test_summarization_empty(graph_type):
      G = graph_type()
      summary_graph = nx.snap_aggregation(G, node_attributes=("color",))
      assert nx.is_isomorphic(summary_graph, G)
  
imports: import pytest
  import networkx
label_desc: Use image node_id 1 for calling a global function with example usage: test_summarization_empty(graph_type) without return types