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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 __visit_index_model_instance(self, models, p, k, v):
 """ Called during model research on merged data """

            # print 'model visit {} on {}'.format(model, v)
        cp = p + (k,)
        for model in models:
            try:
                if model.validator(v):
                    if cp in self.path_index:
                        # if self.path_index[cp].val != v:
                        #     raise ValueError('unexpected value change at path_index[{}]'.format(cp))
                        self.path_index[cp].add_model(model, v)
                    else:
                        # The object should already be in the index but don't complain for now.
                        self.path_index[cp] = PathCacheObject(val=v, path=cp, regs=[model])
            except:
                pass