code: def test_get_parameter_dd(self):
      string = """
          <pomdpx version="1.0" id="rockSample"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="pomdpx.xsd">
           <Description>RockSample problem for map size 1 x 3.
             Rock is at 0, Rover’s initial position is at 1.
             Exit is at 2.
           </Description>
           <Discount>0.95</Discount>
          <InitialStateBelief>
          <CondProb>
           <Var>rover_0</Var>
    <Parent>null</Parent>
     <Parameter type = "DD">
        <DAG>
           <Node var = "rover_0">
               <Edge val="s0"><Terminal>0.0</Terminal></Edge>
                <Edge val="s1">
                   <Node var = "rock_0">
                       <Edge val = "good">
                         <Terminal>0.5</Terminal>
                    </Edge>
                     <Edge val = "bad">
                        <Terminal>0.5</Terminal>
                     </Edge>
                  </Node>
             </Edge>
             <Edge val="s2"><Terminal>0.0</Terminal></Edge>
           </Node>
        </DAG>
    </Parameter>
    </CondProb>
    </InitialStateBelief>
    </pomdpx>
   """
      self.reader_string = PomdpXReader(string=string)
      self.reader_file = PomdpXReader(path=io.StringIO(string))
      expected_dd_parameter = [
          {
              "Var": "rover_0",
              "Parent": ["null"],
              "Type": "DD",
              "Parameter": {
                  "rover_0": {
                      "s0": "0.0",
                      "s1": {"rock_0": {"good": "0.5", "bad": "0.5"}},
                      "s2": "0.0",
                  }
              },
          }
      ]
      self.maxDiff = None
      self.assertEqual(
          expected_dd_parameter,
          self.reader_string.get_initial_beliefs(),
      )
      self.assertEqual(
          expected_dd_parameter, self.reader_file.get_initial_beliefs()
      )
  
imports: import io
  import sys
  import unittest
  import xml.etree.ElementTree
  from pgmpy.readwrite import PomdpXReader, PomdpXWriter
label_desc: Use image node_id 7 for calling the TestPomdpXReaderStringTorch obj's underlying member method code with example usage: obj.test_get_parameter_dd() without return types