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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def __unpack_tgz(self, filename):

 """Unpack the `tar.gz`, `tgz` compressed file format"""

        if isinstance(filename, string_types) and self.__isValidTGZ(filename) and tarfile.is_tarfile(filename):
            with tarfile.open(filename, mode='r:gz') as t:
                for name in t.getnames():
                    t.extract(name, self.plugin_abspath)
        else:
            raise TarError("Invalid Plugin Compressed File")