code: def test_from_networkx_empty():
      g = nx.Graph()
      # no features, means no types
      nodes, edges = from_networkx_for_testing(g)
      assert nodes == {}
      assert edges == {}
  
      # various forms of features:
      nodes, edges = from_networkx_for_testing(g, node_features={})
      assert nodes == {}
      assert edges == {}
  
      features = pd.DataFrame(columns=range(10))
  
      nodes, edges = from_networkx_for_testing(
          g, node_features=features
      )
      assert nodes == {}
      assert edges == {}
  
      nodes, edges = from_networkx_for_testing(
          g, node_features={"b": features}
      )
      assert nodes == {}
      assert edges == {}
  
imports: import networkx
  import numpy
  import pandas
  import pytest
  from stellargraph.core.convert import ColumnarConverter, convert_nodes, convert_edges, from_networkx
  from stellargraph.core.indexed_array import IndexedArray
label_desc: Use image node_id 27 for calling a global function with example usage: test_from_networkx_empty() without return types