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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 prior(self):
 """ Model prior for particular model. Product of eclipse probability (``self.prob``), the fraction of scenario that is allowed by the various constraints (``self.selectfrac``), and all additional factors in ``self.priorfactors``. """

        prior = self.prob * self.selectfrac
        for f in self.priorfactors:
            prior *= self.priorfactors[f]
        return prior