code: def test_double_integral3(self):
      def func(x0, x1):
          return x0 + x1 + 1 + 2
  
      assert_quad(dblquad(func, 1, 2, 1, 2), 6.0)
  
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 15 for calling the TestQuad obj's underlying member method code with example usage: obj.test_double_integral3() and returns: unknown