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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 _default_styles_xml(cls):
 """ Return a bytestream containing XML for a default styles part. """

        path = os.path.join(
            os.path.split(__file__)[0], '..', 'templates',
            'default-styles.xml'
        )
        with open(path, 'rb') as f:
            xml_bytes = f.read()
        return xml_bytes