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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 createManager(self, services, yadis_url=None):
 """Create a new YadisService Manager for this starting URL and suffix, and store it in the session. @raises KeyError: When I already have a manager. @return: A new YadisServiceManager or None """

        key = self.getSessionKey()
        if self.getManager():
            raise KeyError('There is already a %r manager for %r' %
                           (key, self.url))

        if not services:
            return None

        manager = YadisServiceManager(self.url, yadis_url, services, key)
        manager.store(self.session)
        return manager