code: def test_accumulation_middle(self):
      # Set occlusion_layers to all 0, so top splats are co-surface with splatted
      # pixels. Thus, the top splatting layer should be accumulated to surface, and
      # all other layers to background.
      splat_colors_and_weights = torch.rand((1, 1, 1, 3, 9, 5))
      occlusion_layers = torch.zeros((1, 1, 1, 9))
      (
          splatted_colors,
          splatted_weights,
      ) = _compute_splatted_colors_and_weights(
          occlusion_layers, splat_colors_and_weights
      )
  
      # Foreground splats (there are none).
      self.assertClose(
          splatted_colors[0, 0, 0, :, 0],
          torch.zeros((4)),
          atol=0.001,
      )
  
      # Surface splats
      self.assertClose(
          splatted_colors[0, 0, 0, :, 1],
          splat_colors_and_weights[0, 0, 0, 0, :, :4].sum(dim=0),
          atol=0.001,
      )
  
      # Background splats
      self.assertClose(
          splatted_colors[0, 0, 0, :, 2],
          splat_colors_and_weights[0, 0, 0, 1:, :, :4]
          .sum(dim=0)
          .sum(dim=0),
          atol=0.001,
      )
  
imports: import unittest
  import torch
  from pytorch3d.common.compat import meshgrid_ij
  from pytorch3d.renderer.cameras import FoVPerspectiveCameras
  from pytorch3d.renderer.splatter_blend import _compute_occlusion_layers, _compute_splatted_colors_and_weights, _compute_splatting_colors_and_weights, _get_splat_kernel_normalization, _normalize_and_compose_all_layers, _offset_splats, _precompute, _prepare_pixels_and_colors
  from .common_testing import TestCaseMixin
label_desc: Use image node_id 2 for calling the TestComputeSplattedColorsAndWeights obj's underlying member method code with example usage: obj.test_accumulation_middle() without return types