code: def test_added_variable_ols(self, close_figures):
      np.random.seed(3446)
      n = 100
      p = 3
      exog = np.random.normal(size=(n, p))
      lin_pred = 4 + exog[:, 0] + 0.2 * exog[:, 1] ** 2
      endog = lin_pred + np.random.normal(size=n)
  
      model = sm.OLS(endog, exog)
      results = model.fit()
      fig = plot_added_variable(results, 0)
      ax = fig.get_axes()[0]
      ax.set_title("Added variable plot (OLS)")
      close_or_save(pdf, fig)
      close_figures()
  
imports: import numpy
  from numpy.testing import assert_array_less, assert_equal, assert_raises
  from pandas import DataFrame, Series
  import pytest
  import statsmodels.api
  from statsmodels.graphics.regressionplots import abline_plot, add_lowess, influence_plot, plot_added_variable, plot_ccpr, plot_ccpr_grid, plot_ceres_residuals, plot_fit, plot_leverage_resid2, plot_partial_residuals, plot_partregress_grid, plot_regress_exog
label_desc: Use image node_id 1 for calling the TestAddedVariablePlot obj's underlying member method code with example usage: obj.test_added_variable_ols(close_figures) without return types