code: def test_linear_projection_forward():
      idim = 400
      odim = 80
      preencoder = LinearProjection(input_size=idim, output_size=odim)
      x = torch.randn([2, 50, idim], requires_grad=True)
      x_lengths = torch.LongTensor([30, 15])
      y, y_lengths = preencoder(x, x_lengths)
      y.sum().backward()
      assert y.shape == torch.Size([2, 50, odim])
      assert torch.equal(y_lengths, x_lengths)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_linear_projection_forward() without return types