docstr: Tests distortion_factor at the corner case of zero radius.
docstr_tok: ["Tests","distortion_factor","at","the","corner","case","of","zero","radius","."]
code: def test_distortion_factor_preset_zero_radius(self):
      """Tests distortion_factor at the corner case of zero radius."""
      squared_radii = _get_zeros_radii()
      distortion_coefficient = _get_random_coefficient() - 0.5
  
      distortion, mask = quadratic_radial_distortion.distortion_factor(
          squared_radii, distortion_coefficient
      )
  
      with self.subTest(name="distortion"):
          self.assertAllClose(np.ones_like(squared_radii), distortion)
  
      with self.subTest(name="mask"):
          self.assertAllInSet(mask, (False,))
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow
  from tensorflow_graphics.rendering.camera import quadratic_radial_distortion
  from tensorflow_graphics.util import test_case
label_desc: Use image node_id 4 for calling the QuadraticRadialDistortionTest obj's underlying member method code with example usage: obj.test_distortion_factor_preset_zero_radius() without return types