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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 keep_mask(nkeep, X_train, y_train, X_test, y_test, attr_test, model_generator, metric, trained_model, random_state):
 """ The model is revaluated for each test sample with the non-important features set to their mean. """


    X_train, X_test = to_array(X_train, X_test)

    # how many features to mask
    assert X_train.shape[1] == X_test.shape[1]

    # keep nkeep top features for each test explanation
    X_test_tmp = X_test.copy()
    yp_masked_test = np.zeros(y_test.shape)
    tie_breaking_noise = const_rand(X_train.shape[1], random_state) * 1e-6
    mean_vals = X_train.mean(0)
    for i in range(len(y_test)):
        if nkeep[i] < X_test.shape[1]:
            ordering = np.argsort(-attr_test[i,:] + tie_breaking_noise)
            X_test_tmp[i,ordering[nkeep[i]:]] = mean_vals[ordering[nkeep[i]:]]

    yp_masked_test = trained_model.predict(X_test_tmp)

    return metric(y_test, yp_masked_test)