code: def test_filter_forward():
      def filt_func(r, c, sigma=2):
          return (1 / (2 * np.pi * sigma**2)) * np.exp(
              -(r**2 + c**2) / (2 * sigma**2)
          )
  
      gaussian_args = {
          "sigma": 2,
          "preserve_range": True,
          "mode": "constant",
          "truncate": 20  # LPI filtering is more precise than the truncated
          # Gaussian, so don't truncate at the default of 4 sigma
      }
  
      # Odd image size
      image = coins()[:303, :383]
      filtered = filter_forward(image, filt_func)
      filtered_gaussian = gaussian(image, **gaussian_args)
      assert_array_almost_equal(filtered, filtered_gaussian)
  
      # Even image size
      image = coins()
      filtered = filter_forward(image, filt_func)
      filtered_gaussian = gaussian(image, **gaussian_args)
      assert_array_almost_equal(filtered, filtered_gaussian)
  
file_path: scikit-image/skimage/filters/tests/test_lpi_filter.py
imports: import numpy
  import pytest
  from numpy.testing import assert_, assert_equal, assert_array_almost_equal
  from skimage._shared.utils import _supported_float_type
  from skimage.data import camera, coins
  from skimage.filters import LPIFilter2D, filter_inverse, filter_forward, wiener, gaussian
label_desc: Use image node_id 1 for calling a global function with example usage: test_filter_forward() and returns: unknown