code: def test_get_variables(self):
      var_expected = [
          "light-on",
          "bowel-problem",
          "dog-out",
          "hear-bark",
          "family-out",
      ]
      self.assertListEqual(self.reader.get_variables(), var_expected)
  
imports: import os
  import unittest
  import networkx
  import numpy
  import numpy.testing
  from pgmpy import config
  from pgmpy.factors.discrete import TabularCPD
  from pgmpy.models import BayesianNetwork
  from pgmpy.readwrite import BIFReader, BIFWriter
label_desc: Use image node_id 3 for calling the TestBIFReader obj's underlying member method code with example usage: obj.test_get_variables() without return types