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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 ifo(self):
 """ If only one ifo in the ifo_list this will be that ifo. Otherwise an error is raised. """

        if len(self.ifo_list) == 1:
            return self.ifo_list[0]
        else:
            err = "self.ifo_list must contain only one ifo to access the "
            err += "ifo property. %s." %(str(self.ifo_list),)
            raise TypeError(err)