code: def test_sample_texture_atlas(self):
      N, F, R = 1, 2, 2
      verts = torch.randn((4, 3), dtype=torch.float32)
      faces = torch.tensor([[2, 1, 0], [3, 1, 0]], dtype=torch.int64)
      faces_atlas = torch.rand(size=(N, F, R, R, 3))
      tex = TexturesAtlas(atlas=faces_atlas)
      mesh = Meshes(verts=[verts], faces=[faces], textures=tex)
      pix_to_face = torch.tensor([0, 1], dtype=torch.int64).view(
          1, 1, 1, 2
      )
      barycentric_coords = torch.tensor(
          [[0.5, 0.3, 0.2], [0.3, 0.6, 0.1]], dtype=torch.float32
      ).view(1, 1, 1, 2, -1)
      expected_vals = torch.tensor(
          [[0.5, 1.0, 0.3], [0.3, 1.0, 0.9]], dtype=torch.float32
      )
      expected_vals = torch.zeros((1, 1, 1, 2, 3), dtype=torch.float32)
      expected_vals[..., 0, :] = faces_atlas[0, 0, 0, 1, ...]
      expected_vals[..., 1, :] = faces_atlas[0, 1, 1, 0, ...]
  
      fragments = Fragments(
          pix_to_face=pix_to_face,
          bary_coords=barycentric_coords,
          zbuf=torch.ones_like(pix_to_face),
          dists=torch.ones_like(pix_to_face),
      )
      texels = mesh.textures.sample_textures(fragments)
      self.assertTrue(torch.allclose(texels, expected_vals))
  
imports: import unittest
  import torch
  import torch.nn.functional
  from pytorch3d.renderer.mesh.rasterizer import Fragments
  from pytorch3d.renderer.mesh.textures import _list_to_padded_wrapper, TexturesAtlas, TexturesUV, TexturesVertex
  from pytorch3d.renderer.mesh.utils import pack_rectangles, pack_unique_rectangles, Rectangle
  from pytorch3d.structures import list_to_packed, Meshes, packed_to_list
  from .common_testing import TestCaseMixin
  from .test_meshes import init_mesh
label_desc: Use image node_id 1 for calling the TestTexturesAtlas obj's underlying member method code with example usage: obj.test_sample_texture_atlas() without return types