class_docstr: Test the PipelineHelper class.
class_docstr_tok: ["Test","the","PipelineHelper","class","."]
code: def test_join_dict(self):
      chunk = {"x": torch.randn(8, 5), "y": torch.randn(8, 2)}
      chunks = [chunk, chunk]
      j = PipelineHelper.join(chunks)
      assert isinstance(j, dict)
      assert len(j) == 2
      assert "x" in j
      assert "y" in j
      assert isinstance(j["x"], torch.Tensor)
      assert isinstance(j["y"], torch.Tensor)
      assert j["x"].shape == (16, 5)
      assert j["y"].shape == (16, 2)
  
imports: import torch
  import numpy
  import unittest
  from parlai.utils.torch import padded_tensor, argsort, PipelineHelper, neginf, IdentityLayer, trainable_parameters, total_parameters
label_desc: Use image node_id 10 for calling the TestPipelineHelper obj's underlying member method code with example usage: obj.test_join_dict() without return types