def assertNotIsInstance(self, a, b):
        if isinstance(a, b):
            raise AssertionError("{} is instance of {}".format(a, b))
If a duplicate is being installed, skips it.
dataset/ETHPy150Open ga4gh/server/tests/datadriven/__init__.py/TestCase.assertNotIsInstance--crossover with--dataset/ETHPy150Open robmadole/jig/src/jig/commands/tests/test_install.py/TestInstallCommand.test_skips_duplicates