code: def test_double_integral_improper(
      self, x_lower, x_upper, y_lower, y_upper, expected
  ):
      # The Gaussian Integral.
      def f(x, y):
          return np.exp(-(x**2) - y**2)
  
      assert_quad(
          dblquad(f, x_lower, x_upper, y_lower, y_upper),
          expected,
          error_tolerance=3e-8,
      )
  
imports: import sys
  import math
  import numpy
  from numpy import sqrt, cos, sin, arctan, exp, log, pi
  from numpy.testing import assert_, assert_allclose, assert_array_less, assert_almost_equal
  import pytest
  from scipy.integrate import quad, dblquad, tplquad, nquad
  from scipy.special import erf, erfc
  from scipy._lib._ccallback import LowLevelCallable
  import ctypes
  import ctypes.util
  from scipy._lib._ccallback_c import sine_ctypes
  import scipy.integrate._test_multivariate
label_desc: Use image node_id 16 for calling the TestQuad obj's underlying member method code with example usage: obj.test_double_integral_improper(x_lower, x_upper, y_lower, y_upper, expected) and returns: np