ERROR: test_lexicon (__main__.TestLexicon)

[tmlim12345]

can someone helps please?
def suite():
suite = unittest.TestSuite()
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestLexicon))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestFrequency))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestModel))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestMorphology))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestContext))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestEntities))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestParser))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestSentiment))
suite.addTest(unittest.TestLoader().loadTestsFromTestCase(TestMultilingual))
it looks like all the tests cannot be loaded at all.