code: def test_shunting_yard(self):
      actual = _shunting_yard("    x1 +4.2 * ( x2 - 1) ")
      expected = ["x1", "4.2", "x2", "1", "-", "*", "+"]
      self.assertListEqual(actual, expected)
  
file_path: AIX360/tests/rule_induction/trxf/core/test_feature.py
imports: import tokenize
  from unittest import TestCase
  from aix360.algorithms.rule_induction.trxf.core.feature import Feature, _shunting_yard
label_desc: Use image node_id 8 for calling the TestFeature obj's underlying member method code with example usage: obj.test_shunting_yard() without return types