code: def test_initial_belief_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">
                              <SubDAG type="uniform" var="rock_0"/>
                          </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_belief_dd = [
          {
              "Var": "rover_0",
              "Parent": ["null"],
              "Type": "DD",
              "Parameter": {
                  "rover_0": {
                      "s0": "0.0",
                      "s1": {"type": "uniform", "var": "rock_0"},
                      "s2": "0.0",
                  }
              },
          }
      ]
      self.maxDiff = None
      self.assertEqual(
          self.reader_string.get_initial_beliefs(), expected_belief_dd
      )
      self.assertEqual(
          self.reader_file.get_initial_beliefs(), expected_belief_dd
      )
  
imports: import io
  import sys
  import unittest
  import xml.etree.ElementTree
  from pgmpy.readwrite import PomdpXReader, PomdpXWriter
label_desc: Use image node_id 8 for calling the TestPomdpXReaderString obj's underlying member method code with example usage: obj.test_initial_belief_dd() without return types