code: def test_frontend_backward(train):
      frontend = AsteroidFrontend(
          sinc_filters=16,
          sinc_kernel_size=128,
          sinc_stride=16,
      )
      if train:
          frontend.train()
      else:
          frontend.eval()
      set_all_random_seed(14)
      x = torch.randn(2, 1000, requires_grad=True)
      x_lengths = torch.LongTensor([1000, 980])
      y, y_lengths = frontend(x, x_lengths)
      y.sum().backward()
  
imports: import pytest
  import torch
  from espnet2.asr.frontend.asteroid_frontend import AsteroidFrontend
  from espnet2.torch_utils.set_all_random_seed import set_all_random_seed
label_desc: Use image node_id 3 for calling a global function with example usage: test_frontend_backward(train) without return types