docstr: Test SetVariable and GetVariableAsString.
docstr_tok: ["Test","SetVariable","and","GetVariableAsString","."]
code: def test_variables(self):
      """Test SetVariable and GetVariableAsString."""
      self._api.SetVariable("debug_file", "/dev/null")
      self.assertEqual(
          self._api.GetVariableAsString("debug_file"), "/dev/null"
      )
  
imports: import unittest
  import re
  import os.path
  import tesserocr
label_desc: Use image node_id 12 for calling the TestTessBaseApi obj's underlying member method code with example usage: obj.test_variables() without return types