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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_zip(self, filename):

 """Unpack the `zip` compressed file format"""

        if isinstance(filename, string_types) and self.__isValidZIP(filename) and zipfile.is_zipfile(filename):
            with zipfile.ZipFile(filename) as z:
                for name in z.namelist():
                    z.extract(name, self.plugin_abspath)
        else:
            raise ZipError("Invalid Plugin Compressed File")