code: def test_forward():
      layer = Stft(win_length=4, hop_length=2, n_fft=4)
      x = torch.randn(2, 30)
      y, _ = layer(x)
      assert y.shape == (2, 16, 3, 2)
      y, ylen = layer(x, torch.tensor([30, 15], dtype=torch.long))
      assert (ylen == torch.tensor((16, 8), dtype=torch.long)).all()
  
imports: import torch
  from espnet2.layers.stft import Stft
label_desc: Use image node_id 2 for calling a global function with example usage: test_forward() without return types