code: def test_torch_4d(self):
      collator = Collator(backend="torch")
      data = [{"x": [[[0, 1], [2, 3]]]}, {"x": [[[0, 1]]]}]
      output = collator(data)
      assert output["x"].size() == (2, 1, 2, 2)
  
imports: import numpy
  import pytest
  from fastNLP.envs.imports import _NEED_IMPORT_TORCH, _NEED_IMPORT_PADDLE, _NEED_IMPORT_JITTOR, _NEED_IMPORT_ONEFLOW
  from fastNLP.core.collators.collator import Collator
  from ...helpers.utils import Capturing
label_desc: Use image node_id 9 for calling the TestCollator obj's underlying member method code with example usage: obj.test_torch_4d() without return types