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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 add_population(self,pop):
 """Adds population to PopulationSet """

        if pop.model in self.modelnames:
            raise ValueError('%s model already in PopulationSet.' % pop.model)
        self.modelnames.append(pop.model)
        self.shortmodelnames.append(pop.modelshort)
        self.poplist.append(pop)