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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 section_by_title( self, title: str, ) -> Optional[WikipediaPageSection]: """ Returns section of the current page with given `title`. :param title: section title :return: :class:`WikipediaPageSection` """

        if not self._called['extracts']:
            self._fetch('extracts')
        return self._section_mapping.get(title)