code: def test_get_edges(self):
      self.assertListEqual(
          self.reader_string.get_edges(),
          [("a", "b"), ("a", "c"), ("b", "d"), ("c", "d"), ("c", "e")],
      )
      self.assertListEqual(
          self.reader_file.get_edges(),
          [("a", "b"), ("a", "c"), ("b", "d"), ("c", "d"), ("c", "e")],
      )
  
imports: import io
  import sys
  import unittest
  import xml.etree.ElementTree
  import networkx
  import numpy
  import numpy.testing
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.models import BayesianNetwork
  from pgmpy.readwrite import XMLBeliefNetwork
label_desc: Use image node_id 7 for calling the TestXBNReader obj's underlying member method code with example usage: obj.test_get_edges() without return types