def METHOD_NAME(data):
    mod = PooledOLS(data.y, data.x)
    y = PanelData(data.y)
    entity_clusters = pd.DataFrame(y.entity_ids, index=y.index)
    vc1 = PanelData(data.vc1)
    clusters = vc1.copy()
    clusters.dataframe["var.cluster.entity"] = entity_clusters
    clusters._frame = clusters._frame.astype(np.int64)
    res = mod.fit(cov_type="clustered", clusters=clusters, debiased=False)
    y = mod.dependent.dataframe.copy()
    x = mod.exog.dataframe.copy()
    y.index = np.arange(len(y))
    x.index = y.index
    clusters = mod.reformat_clusters(clusters)
    ols_mod = IV2SLS(y, x, None, None)
    ols_res = ols_mod.fit(cov_type="clustered", clusters=clusters.dataframe)
    assert_results_equal(res, ols_res)