code: def test_frontend_backward():
      frontend = FusedFrontends(
          fs="16k",
          align_method="linear_projection",
          proj_dim=100,
          frontends=list_frontends,
      )
      x = torch.randn(2, 300, requires_grad=True)
      x_lengths = torch.LongTensor([300, 89])
      y, y_lengths = frontend(x, x_lengths)
      y.sum().backward()
  
imports: import torch
  from espnet2.asr.frontend.fused import FusedFrontends
label_desc: Use image node_id 3 for calling a global function with example usage: test_frontend_backward() without return types