code: def test_validate(self):
      model = ModelHelper(name="test_model")
      model.params.append("aaa")
      model.params.append("bbb")
      self.assertEqual(model._Validate(), [])
  
      model.params.append("xxx")
      model.params.append("bbb")
      self.assertEqual(model._Validate(), ["bbb"])
  
imports: from caffe2.python import brew, core, scope, workspace
  from caffe2.python.modeling.parameter_info import ParameterTags
  from caffe2.python.model_helper import ModelHelper
  from caffe2.python.cnn import CNNModelHelper
  import unittest
  import numpy
label_desc: Use image node_id 6 for calling the BrewTest obj's underlying member method code with example usage: obj.test_validate() without return types