code: def setUp(self):
      self.N, self.H, self.W, self.K = 2, 3, 4, 5
      self.pixel_coords_screen = (
          torch.stack(
              meshgrid_ij(torch.arange(self.H), torch.arange(self.W)),
              dim=-1,
          )
          .reshape(1, self.H, self.W, 1, 2)
          .expand(self.N, self.H, self.W, self.K, 2)
          .float()
          + 0.5
      )
      self.colors = torch.ones((self.N, self.H, self.W, self.K, 4))
  
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 1 for calling the TestComputeSplattingColorsAndWeights obj's underlying member method code with example usage: obj.setUp() without return types