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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 merge(self, ds, inplace=False, axis=1):
 """Merge two datasets. Parameters axis : {0,1} ds : `Dataset` inplace : bool, default False Returns ------- `Dataset` """

        if not isinstance(ds, Dataset):
            raise ValueError('Expected `Dataset`, got %s.' % ds)

        X_train = concat(ds.X_train, self.X_train, axis=axis)
        y_train = concat(ds.y_train, self.y_train, axis=axis)

        if ds.X_test is not None:
            X_test = concat(ds.X_test, self.X_test, axis=axis)
        else:
            X_test = None

        if ds.y_test is not None:
            y_test = concat(ds.y_test, self.y_test, axis=axis)
        else:
            y_test = None

        if inplace:
            self._X_train = X_train
            self._y_train = y_train

            if X_test is not None:
                self._X_test = X_test

            if y_test is not None:
                self._y_test = y_test

            return None

        return Dataset(X_train, y_train, X_test, y_test)