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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 _styles_part(self):
 """ Instance of |StylesPart| for this document. Creates an empty styles part if one is not present. """

        try:
            return self.part_related_by(RT.STYLES)
        except KeyError:
            styles_part = StylesPart.default(self.package)
            self.relate_to(styles_part, RT.STYLES)
            return styles_part