code: def test_get_variables(self):
      var_expected = {
          "StateVar": [
              {
                  "vnamePrev": "rover_0",
                  "vnameCurr": "rover_1",
                  "ValueEnum": ["s0", "s1", "s2"],
                  "fullyObs": True,
              },
              {
                  "vnamePrev": "rock_0",
                  "vnameCurr": "rock_1",
                  "fullyObs": False,
                  "ValueEnum": ["good", "bad"],
              },
          ],
          "ObsVar": [
              {"vname": "obs_sensor", "ValueEnum": ["ogood", "obad"]}
          ],
          "RewardVar": [{"vname": "reward_rover"}],
          "ActionVar": [
              {
                  "vname": "action_rover",
                  "ValueEnum": ["amw", "ame", "ac", "as"],
              }
          ],
      }
      self.maxDiff = None
      self.assertEqual(self.reader_string.get_variables(), var_expected)
      self.assertEqual(self.reader_file.get_variables(), var_expected)
  
imports: import io
  import sys
  import unittest
  import xml.etree.ElementTree
  from pgmpy.readwrite import PomdpXReader, PomdpXWriter
label_desc: Use image node_id 2 for calling the TestPomdpXReaderString obj's underlying member method code with example usage: obj.test_get_variables() without return types