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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_priorfactor(self,**kwargs):
 """Adds given values to priorfactors If given keyword exists already, error will be raised to use :func:`EclipsePopulation.change_prior` instead. """

        for kw in kwargs:
            if kw in self.priorfactors:
                logging.error('%s already in prior factors for %s.  use change_prior function instead.' % (kw,self.model))
                continue
            else:
                self.priorfactors[kw] = kwargs[kw]
                logging.info('%s added to prior factors for %s' % (kw,self.model))