code: def test_file(self):
      self.expected_xml = etree.XML(
          """<ANALYSISNOTEBOOK>
    <BNMODEL>
      <VARIABLES>
        <VAR NAME="a" TYPE="discrete" XPOS="13495" YPOS="10465">
          <DESCRIPTION DESCRIPTION="(a) Metastatic Cancer"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
        <VAR NAME="b" TYPE="discrete" XPOS="11290" YPOS="11965">
          <DESCRIPTION DESCRIPTION="(b) Serum Calcium Increase"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
        <VAR NAME="c" TYPE="discrete" XPOS="15250" YPOS="11935">
          <DESCRIPTION DESCRIPTION="(c) Brain Tumor"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
        <VAR NAME="d" TYPE="discrete" XPOS="13960" YPOS="12985">
          <DESCRIPTION DESCRIPTION="(d) Coma"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
        <VAR NAME="e" TYPE="discrete" XPOS="17305" YPOS="13240">
          <DESCRIPTION DESCRIPTION="(e) Papilledema"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
        <VAR NAME="f" TYPE="discrete" XPOS="13440" YPOS="10489">
          <DESCRIPTION DESCRIPTION="(f) Asthma"/>
          <STATENAME>Present</STATENAME>
          <STATENAME>Absent</STATENAME>
        </VAR>
      </VARIABLES>
      <STRUCTURE>
        <ARC CHILD="b" PARENT="a"/>
        <ARC CHILD="c" PARENT="a"/>
        <ARC CHILD="d" PARENT="b"/>
        <ARC CHILD="d" PARENT="c"/>
        <ARC CHILD="e" PARENT="c"/>
      </STRUCTURE>
      <DISTRIBUTIONS>
        <DIST TYPE="discrete">
          <PRIVATE NAME="a"/>
          <DPIS>
            <DPI> 0.2 0.8 </DPI>
          </DPIS>
        </DIST>
        <DIST TYPE="discrete">
          <PRIVATE NAME="b"/>
          <DPIS>
            <DPI INDEXES=" 0 "> 0.8 0.2 </DPI>
            <DPI INDEXES=" 1 "> 0.2 0.8 </DPI>
          </DPIS>
          <CONDSET>
            <CONDELEM NAME="a"/>
          </CONDSET>
        </DIST>
        <DIST TYPE="discrete">
          <PRIVATE NAME="c"/>
          <DPIS>
            <DPI INDEXES=" 0 "> 0.2 0.8 </DPI>
            <DPI INDEXES=" 1 "> 0.05 0.95 </DPI>
          </DPIS>
          <CONDSET>
            <CONDELEM NAME="a"/>
          </CONDSET>
        </DIST>
        <DIST TYPE="discrete">
          <PRIVATE NAME="d"/>
          <DPIS>
            <DPI INDEXES=" 0 0 "> 0.8 0.2 </DPI>
            <DPI INDEXES=" 0 1 "> 0.9 0.1 </DPI>
            <DPI INDEXES=" 1 0 "> 0.7 0.3 </DPI>
            <DPI INDEXES=" 1 1 "> 0.05 0.95 </DPI>
          </DPIS>
          <CONDSET>
            <CONDELEM NAME="b"/>
            <CONDELEM NAME="c"/>
          </CONDSET>
        </DIST>
        <DIST TYPE="discrete">
          <PRIVATE NAME="e"/>
          <DPIS>
            <DPI INDEXES=" 0 "> 0.8 0.2 </DPI>
            <DPI INDEXES=" 1 "> 0.6 0.4 </DPI>
          </DPIS>
          <CONDSET>
            <CONDELEM NAME="c"/>
          </CONDSET>
        </DIST>
        <DIST TYPE="discrete">
          <PRIVATE NAME="f"/>
          <DPIS>
            <DPI> 0.3 0.7 </DPI>
          </DPIS>
        </DIST>
      </DISTRIBUTIONS>
    </BNMODEL>
  </ANALYSISNOTEBOOK>"""
      )
      output = str(self.writer.__str__())
      expected = str(etree.tostring(self.expected_xml))
      self.assertEqual(
          str(self.writer.__str__()[:-1]),
          str(etree.tostring(self.expected_xml)),
      )
  
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 2 for calling the TestXBNWriterTorch obj's underlying member method code with example usage: obj.test_file() without return types