class_docstr: Test IO operations on homogeneous EPGM graphs
docstr: Test the .node_types() method
docstr_tok: ["Test","the",".node_types","(",")","method"]
code: def test_node_types(self):
      """Test the .node_types() method"""
      G_epgm = EPGM(self.input_dir)
      graph_id = G_epgm.G["graphs"][0]["id"]
  
      # cora has a single 'paper' node type:
      node_types = G_epgm.node_types(graph_id)
  
      assert len(node_types) == 1
      assert self.node_type in node_types
  
      with pytest.raises(Exception):
          G_epgm.node_types("invalid_graph_id")
  
file_path: stellargraph/tests/data/test_epgm.py
imports: import pytest
  import os
  import numpy
  from stellargraph.data.epgm import EPGM
label_desc: Use image node_id 2 for calling the Test_EPGM_IO_Homogeneous obj's underlying member method code with example usage: obj.test_node_types() without return types