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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 _impute_values(self, features):
 """Impute missing values in a feature set. Parameters features: array-like {n_samples, n_features} A feature matrix Returns ------- array-like {n_samples, n_features} """

        if self.verbosity > 1:
            print('Imputing missing values in feature set')

        if self._fitted_imputer is None:
            self._fitted_imputer = Imputer(strategy="median")
            self._fitted_imputer.fit(features)

        return self._fitted_imputer.transform(features)