code: def test_pack_traces():
      traces, types = (
          np.array(
              [[0, 1, -1, -1, -1, -1, -1], [0, 1, 1, 3, 0, 0, 0]],
              dtype="int64",
          ),
          np.array([0, 0, 1, 0, 0, 1, 0], dtype="int64"),
      )
      traces = F.zerocopy_from_numpy(traces)
      types = F.zerocopy_from_numpy(types)
      result = dgl.sampling.pack_traces(traces, types)
      assert F.array_equal(
          result[0],
          F.tensor([0, 1, 0, 1, 1, 3, 0, 0, 0], dtype=F.int64),
      )
      assert F.array_equal(
          result[1],
          F.tensor([0, 0, 0, 0, 1, 0, 0, 1, 0], dtype=F.int64),
      )
      assert F.array_equal(result[2], F.tensor([2, 7], dtype=F.int64))
      assert F.array_equal(result[3], F.tensor([0, 2], dtype=F.int64))
  
imports: import unittest
  import warnings
  import backend
  import dgl
  import numpy
  import pytest
label_desc: Use image node_id 5 for calling a global function with example usage: test_pack_traces() without return types