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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(self, model):
 """Add a index method. This method is used to add index algorithms. If multiple algorithms are added, the union of the record pairs from the algorithm is taken. Parameters model : list, class A (list of) index algorithm(s) from :mod:`recordlinkage.index`. """

        if isinstance(model, list):
            self.algorithms = self.algorithms + model
        else:
            self.algorithms.append(model)