code: def test_malformed_expression_should_raise(self):
      missing_op = "   5 +x1     (4-x2)"
      self.assertRaises(ValueError, Feature, missing_op)
  
      empty_expression = ""
      self.assertRaises(ValueError, Feature, empty_expression)
  
      unmatched_parenthesis = "   5 +x1  *  (4-x2))"
      self.assertRaises(
          tokenize.TokenError, Feature, unmatched_parenthesis
      )
  
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 6 for calling the TestFeature obj's underlying member method code with example usage: obj.test_malformed_expression_should_raise() without return types