code: def returning_zeros_brdf(
      incoming_light_direction,
      outgoing_light_direction,
      surface_point_normal,
  ):
      del incoming_light_direction, outgoing_light_direction  # Unused.
      return tf.zeros_like(surface_point_normal)
  
file_path: graphics/tensorflow_graphics/rendering/light/tests/point_light_test.py
imports: import math
  from absl.testing import flagsaver
  from absl.testing import parameterized
  import numpy
  import tensorflow
  from tensorflow_graphics.rendering.light import point_light
  from tensorflow_graphics.util import test_case
label_desc: Use image node_id 2 for calling a global function with example usage: returning_zeros_brdf(incoming_light_direction, outgoing_light_direction, surface_point_normal) and returns: tf