code: def test_dblint():
      # Basic test to see it runs and gives the correct result on a trivial
      # problem. Note that `dblint` is not exposed in the interpolate namespace.
      x = np.linspace(0, 1)
      y = np.linspace(0, 1)
      xx, yy = np.meshgrid(x, y)
      rect = RectBivariateSpline(x, y, 4 * xx * yy)
      tck = list(rect.tck)
      tck.extend(rect.degrees)
  
      assert_almost_equal(dblint(0, 1, 0, 1, tck), 1)
      assert_almost_equal(dblint(0, 0.5, 0, 1, tck), 0.25)
      assert_almost_equal(dblint(0.5, 1, 0, 1, tck), 0.75)
      assert_almost_equal(dblint(-100, 100, -100, 100, tck), 1)
  
imports: import itertools
  import os
  import numpy
  from numpy.testing import assert_equal, assert_allclose, assert_, assert_almost_equal, assert_array_almost_equal
  from pytest import raises
  import pytest
  from scipy._lib._testutils import check_free_memory
  from scipy.interpolate import RectBivariateSpline
  from scipy.interpolate._fitpack_py import splrep, splev, bisplrep, bisplev, sproot, splprep, splint, spalde, splder, splantider, insert, dblint
  from scipy.interpolate.dfitpack import regrid_smth
  from scipy.interpolate._fitpack2 import dfitpack_int
label_desc: Use image node_id 5 for calling a global function with example usage: test_dblint() without return types