code: def setUp(self):
      config.set_backend("torch")
  
      reader = XMLBIFReader(string=TEST_FILE)
      self.expected_model = reader.get_model()
      self.writer = XMLBIFWriter(self.expected_model)
  
      self.model_stateless = BayesianNetwork(
          [("D", "G"), ("I", "G"), ("G", "L"), ("I", "S")]
      )
      self.cpd_d = TabularCPD(
          variable="D", variable_card=2, values=[[0.6], [0.4]]
      )
      self.cpd_i = TabularCPD(
          variable="I", variable_card=2, values=[[0.7], [0.3]]
      )
  
      self.cpd_g = TabularCPD(
          variable="G",
          variable_card=3,
          values=[
              [0.3, 0.05, 0.9, 0.5],
              [0.4, 0.25, 0.08, 0.3],
              [0.3, 0.7, 0.02, 0.2],
          ],
          evidence=["I", "D"],
          evidence_card=[2, 2],
      )
  
      self.cpd_l = TabularCPD(
          variable="L",
          variable_card=2,
          values=[[0.1, 0.4, 0.99], [0.9, 0.6, 0.01]],
          evidence=["G"],
          evidence_card=[3],
      )
  
      self.cpd_s = TabularCPD(
          variable="S",
          variable_card=2,
          values=[[0.95, 0.2], [0.05, 0.8]],
          evidence=["I"],
          evidence_card=[2],
      )
  
      self.model_stateless.add_cpds(
          self.cpd_d, self.cpd_i, self.cpd_g, self.cpd_l, self.cpd_s
      )
      self.writer_stateless = XMLBIFWriter(self.model_stateless)
  
imports: import os
  import unittest
  import xml.etree.ElementTree
  import numpy
  import numpy.testing
  from pgmpy import config
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.models import BayesianNetwork
  from pgmpy.readwrite import XMLBIFReader, XMLBIFWriter
label_desc: Use image node_id 1 for calling the TestXMLBIFWriterMethodsString obj's underlying member method code with example usage: obj.setUp() without return types