code: def test_split_data_keep_connected_parameter(
      self, heterogeneous_graph
  ):
      g, es_obj = heterogeneous_graph
  
      # keep_connected must be bool type.
      with pytest.raises(ValueError):
          es_obj.train_test_split(keep_connected="Yes")
  
      with pytest.raises(ValueError):
          es_obj.train_test_split(keep_connected=0)
  
      with pytest.raises(ValueError):
          es_obj.train_test_split(keep_connected=None)
  
imports: import pytest
  import os
  import numpy
  import networkx
  from stellargraph import StellarGraph
  from stellargraph.data.edge_splitter import EdgeSplitter
  from stellargraph.data.epgm import EPGM
  import random
  import datetime
  from datetime import datetime, timedelta
  from ..test_utils import flaky_xfail_mark
  from ..test_utils.graphs import example_graph_random
label_desc: Use image node_id 1 for calling the TestEdgeSplitterCommon obj's underlying member method code with example usage: obj.test_split_data_keep_connected_parameter(heterogeneous_graph) without return types