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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 feature(self, index):
 """ Returns a feature. Parameters index : int index of feature in list Returns ------- :obj:`Feature` """

        if index < 0 or index >= self.num_features_:
            raise ValueError('Index %d out of range' %(index))
        return self.features_[index]