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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 setup(self):
 """ Performs some checks. :return: None if successful, otherwise error message. :rtype: str """

        result = super(BranchDirector, self).setup()
        if result is None:
            try:
                self.check_actors()
            except Exception, e:
                result = str(e)
        return result