code: def test_obs_function(self):
      obs_function_expected = [
          {
              "Var": "obs_sensor",
              "Parent": ["action_rover", "rover_1", "rock_1"],
              "Type": "TBL",
              "Parameter": [
                  {
                      "Instance": ["amw", "*", "*", "-"],
                      "ProbTable": ["1.0", "0.0"],
                  },
                  {
                      "Instance": ["ame", "*", "*", "-"],
                      "ProbTable": ["1.0", "0.0"],
                  },
                  {
                      "Instance": ["as", "*", "*", "-"],
                      "ProbTable": ["1.0", "0.0"],
                  },
                  {
                      "Instance": ["ac", "s0", "-", "-"],
                      "ProbTable": ["1.0", "0.0", "0.0", "1.0"],
                  },
                  {
                      "Instance": ["ac", "s1", "-", "-"],
                      "ProbTable": ["0.8", "0.2", "0.2", "0.8"],
                  },
                  {
                      "Instance": ["ac", "s2", "*", "-"],
                      "ProbTable": ["1.0", "0.0"],
                  },
              ],
          }
      ]
      self.maxDiff = None
      self.assertEqual(
          self.reader_string.get_obs_function(), obs_function_expected
      )
      self.assertEqual(
          self.reader_file.get_obs_function(), obs_function_expected
      )
  
imports: import io
  import sys
  import unittest
  import xml.etree.ElementTree
  from pgmpy.readwrite import PomdpXReader, PomdpXWriter
label_desc: Use image node_id 5 for calling the TestPomdpXReaderString obj's underlying member method code with example usage: obj.test_obs_function() without return types