code: def test_decimation_basic():
      N_1, N_2 = 4, 6
      decimation_factor = 2
      ptr = torch.tensor([0, N_1, N_1 + N_2])
  
      idx_decim, ptr_decim = decimation_indices(ptr, decimation_factor)
  
      expected_size = (N_1 // decimation_factor) + (
          N_2 // decimation_factor
      )
      assert idx_decim.size(0) == expected_size
  
      expected = torch.tensor(
          [0, N_1 // decimation_factor, expected_size]
      )
      assert torch.equal(ptr_decim, expected)
  
imports: import torch
  from torch_geometric.nn.pool.decimation import decimation_indices
label_desc: Use image node_id 1 for calling a global function with example usage: test_decimation_basic() without return types