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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 _call_custom_creator(self, config):
 """ Call a custom driver creator. :param config: The driver configuration :type config: dict :rtype: Repository """

        creator = self._custom_creators[config['driver']](config)

        if isinstance(creator, Store):
            creator = self.repository(creator)

        if not isinstance(creator, Repository):
            raise RuntimeError('Custom creator should return a Repository instance.')

        return creator